Given that GoG has a very specific no DRM at all copy to as many PCs as you own policy I thought I'd do a bit of a search around the net.....
To my joy although the usual suspects have all the retail DRM'd games up the wazoo the gog games appear not to have spread to less than reputable sites....
So despite that there is no DRM and in fact there is a single executable to make it ultra easy.... people seem to be doing the right thing so far as GoG is concerned! Which also puts perspective to the claims that if they didn't have DRM they would lose their sales.... hmm....
So three cheers for GoG and the fantastic community and here's to an astounding 2010 and no doubt some excellent releases and materials through it!

Any claim that DRM works is blown to hell by the fact that there isn't a game out there that isn't cracked.

Yeah three cheers to Good ol' GOG!

The counter-argument being that DRM is not meant to be 100% fool-proof, but instead to discourage the average computer user (not us...) from piracy. That means making things more complex than just copying a disc (or even grabbing a cracked executable).
People tend to make the assumption that DRM is supposed to stop everyone. In actuality, it is a lot like gun control laws (and about as effective :p). The people who are going to do "bad stuff" will get their firearms illegally. But the people who might just commit a crime of passion are much more discouraged.

The funny thing there being in principle GoG installers being a single exe to copy somewhere with no DRM should facilitate this - make it easy for joe-nobody to give to mates... but it doesn't appear to be happening.

Oh, it happens. If you honestly think it doesn't, you are much less cynical than me :p
That being said, it IS true that they don't tend to pop up on warez sites. The reasons for this are twofold:
1. Most people are still afraid that there might be something in the executable to link them to it. Basically, DRM through the threat of DRM :p. This works because people don't actually know what DRM is, and think it is only activation models and Starforce.
2. There is no need. All the GoG games have already been cracked to hell, and most of them are already available in handy-dandy cutdown rips. So all the GoG release would be is another Release floating around.
If the profits are worthwhile for CD Projekt/GoG (and they seem to be), then the DRM wasn't needed. And that is really it. The reason why there is no need for DRM is because it would be like locking a window while leaving the door wide open.
But you can't really use the GoG results to apply to other Digital Distribution services, and you REALLY can't use it for new releases.

Piracy is most rampant and has the biggest consequences for publishers and developers when the games are new. GoG is selling older, mostly "off-the-radar" games (or hidden gems as we like to call them), and there is much less piracy of such titles. For one thing, many are older niche titles with no appeal for the average teenage gamer of today. Second, a would-be pirate must first gain access to the game files to pirate it, and for digitally distributed games that means buying it first. But pirates don't really buy games or they wouldn't be pirates, so even if there is no DRM attached the rate of piracy of GoG games will be very low.

This may have been true back when the preferred method of piracy was burning a copy of the game CD, but this hasn't been the case for several years now. With the ubiquity of broadband and the existence of torrents being common knowledge among the vast majority of those who play PC games the cracked copy from a torrent site is by far the preferred method these days, and DRM does very little to deter this beyond the first week (and even that estimate is being extremely generous).
As for why GOG installers don't seem to be showing up for download in any significant numbers, I think there are several factors that play into this. These are games that have been out for a long time, and that already have numerous pirated versions available, which reduces the motivation to put up new copies for download. The games are available at very low prices with pretty much no hassle; the demand curve at $6-10 doesn't really differ that much from the demand curve at "free" under these conditions. As there's no DRM to crack there's not any street cred to be had by putting up the GOG installers for download, again reducing the motivation to do such. GOG treats their customers very well; I may just be being a naive idealist here, but I do think that when a business treats its customers well the bulk of those customers will return that good will, again greatly reducing the motivation for people to make the installers available for download.

I did some searching too a while back out of curiosity. Found 1 supposed one on a P2P site, but didn't download and check. 99.9% of the games on here aren't pirated as far as I can tell!

I agree with everything you said except this. Have you ever done tech support? The average computer user is still VERY incompetent. Don't think in terms of yourself, think in terms of your grandmother, or your uncle who actually double-clicks "Free Porn.exe". Those are the people that DRM is primarily targetting and it is still very effective at encouraging them to buy. Even competent users are still wary of potentials for viruses in the cracks, so imagine the people who aren't even going to the "reputable" sites.
As for the first week argument: Yeah, basically. But take a look at Mass Effect PC (one of the first two games to use activation model Securom). All the Release Groups tried to crack that, got rid of the basic DRM check, then left. (Un)fortunately, people still couldn't play the game due to a bug that cropped up in the hack-job. A LOT of people bought that game because they really wanted to play and thought it would never be fixed (hell, I think the cracks for that game STILL have issues with regard to the DLCs). There have been a few other games that never really got properly cracked. Few and far between, but it is at least something.
And honestly, that is why developers no longer care about SP anywhere near as much as MP. People are going to crack SP. But if they want to use ranked servers, they need a legit copy for MP. So win-win.
Like I said, gun control or anti-drug laws. People are still going to shoot people and/or get high (hopefully not at the same time :p). But for the everyman, they work. Do those laws inconvenience people? Gun enthusiasts and people who ACTUALLY need medical marijuana for their glaucoma would say yes (just like we say yes when we scream about limited activation models). But, at the same time, a lot of people are discouraged. And that is all you can really hope for.

DRM is a waste of money for publishers, but it makes them feel good. I think DRM is not aimed at hardcore pirates, but the casual pirate. You know the buddy that copies the game for you, or taking disk around to a friends house so you both can play the game.
In that sense it likely works well, but the bottom line is that only the legitimate user is inconvenienced or harmed by DRM.
I pass on all DRM laden Games no matter how good people say they are (Torchlight as an example).

I also buy no games with any form of DRM. It's like paying someone to infect your system with a virus. . . . =)

I haven't done tech support beyond fixing up the family PC and helping some friends back in college, but if you are basing your perception of most computer users on what you see in people calling up tech support then I'd call that the mother of all sample biases. But beyond that, how much complexity do you think is actually being added for pirates when using DRM beyond a simple disc check? If you can't pop the disc into the drive, fire up Nero, and just hit "Copy", then that stops everyone who isn't willing or able to go beyond that. But for everyone who is, simply heading over to a torrent tracker is pretty much the next easiest thing to do. So again, how is all the extra complexity and hassle deterring pirates when both the simple disc check and activation model protected games both end up on torrent sites in about the same amount of time?
As for your claim that DRM encourages people to buy, you're making the same mistake as the folks in the gaming industry who failed Econ 101 in assuming that the demand for a game at $50 is the same as the demand for a game at $0. Regardless of whether DRM can deter some amount of piracy, it says nothing of whether people will be willing to buy the game, and generally I'd contend that the overlap between people looking to pirate the game and people willing to buy the game at $50 is pretty damn small.
So basically the gaming industry got lucky on one game. Out of hundreds. I must say I'm quite unimpressed. Also, do you have any data to back up the claim that some meaningful number of people who would have otherwise pirated the game bought it as a result (keeping in mind that "data" is not the plural of "anecdote")?
I'll say the same thing to this that I ultimately say to everyone who focuses on the piracy-prevention aspect of DRM: you're doing it wrong. It's not about what people will or won't be able to crack, it's about what people will or won't be willing to buy. You could make a multiplayer game that people can't crack, but that doesn't mean much if only half the number of people are willing to buy it than would have if there was a large single-player component to it. No matter how many obstacles you provide to prevent people from pirating games it's all meaningless if you don't provide what's actually import: reasons for people to buy games, and over-aggressive DRM actually works against this.
The whole war on drugs has been one of the biggest clusterfucks the US has ever engaged in. So maybe it will be a rather apt analogy for the DRM situation. Let me just say for the record that I think quite a few drugs should be legalized (and also for the record I don't use any drugs), and I am also a strong supporter of the right of the people to keep and bear arms. But in the interests of not derailing this thread I won't say anything more about either of these matters.

That's not always correct. First, GOG releases tend to be more convenient, especially when it comes to DOS games. GOG are no wizards, of course, but they do seem to take care of basic compatibility issues, so that could save some time.
On the other hand, GOG releases may be worse than actual CD/DVD images, especially when it comes to modding. GOG games are already patched, and some popular mods require either unpatched games or some specific patches, which may not be the latest ones. But that is a minor nuisance.
Anyway, you're quite right when you say that GOG distribution methods can only work for old games.

I saw a guy on a private P2P site I used to frequent who had upped a few GOGs, saying he wanted to "promote" the service. He said he was stopping after a certain amount of games or something.
...interesting approach.
Anyway, I respect the opinions of those who don't buy DRM games, and I did the same for a long time, but to be honest I got tired of missing out on some amazing games. And turns out those amazing games had no negative effect (that I could notice at least) on my system. As for online activation, I can usually crack that with no ill effects if necessary. So...I buy most games I want now. Although if they do have online activation, I will likely wait until I see them on sale (I bought Bioshock for $5 recently, for example).