Yes, for physical goods.
gog has digital goods

Valve has an automated refund system for Steam now and it was not abused although people did the same thing as you did and predicted a horror. What makes you think that a system that needs approval from a real human is more abused than an automated system?

I advice you to try reading Kahneman's book, Thinking, Fast and Slow.

At least in the EU since 2014 it also covers digital goods, as long as they haven't been downloaded yet. Since GOG is located in the EU I suppose they have to obey this law.

I wonder if ACCC intervention had any part in the new system. They're always up valve for not complying with Aussie consumer rights.

Possible, but if gamers swallowed regional prices and many other crap, I think they had swallowed Australia only refunds also. Steam is very big now, they're like Windows for desktop OSes or Google for search engines, so they probably thought that the money will come back to them anyway.

Where did it lie? There's no official list of games available in the piñata (tracker thread is done by the community and not legally binding for GOG)! And all it says in the FAQ is that you won't get doubles as long as there's a game available in the piñata that you don't own already. If Dreamfall and Republique are "sold out" and you own all the other 23 games, then there's no game in the piñata that you don't own already and you get a gift code.

No false advertising here. You're just mixing things that don't belong together (GOG's sale + community's tracker thread). There's no official word about the available games, thus there's no need to mention limited quantities of certain games either. Something's sold out? It's not in the piñata anymore.

As for the rest: Lots of users got fast support initially, before it came to a sudden halt. This happens every single sale when support gets flooded with tickets. You'll get your refund. It'll just take some time since your ticket isn't more important than the other tickets with the same requests.

On the one hand GOG seems to just have technical difficulties with the prevention of doubles (this is not the fault of the support, they rather try to fix it) and on the other hand GOG should more clearly state if the usual 14 days return right (if you did not download the game) applies or doesn't apply to them. It may be they are legally obliged to actually give that right to the customer. In that case they must also say it and not just remain silent about it. If they did not tell the customer about all their rights, they indeed might be acting shady.

You can effectively lose everything here. AFAIK there's no requirement that you lose everything in order for it to be gambling. You just need to put up a wager and have a result that's based on random chance. By convention you'll be losing money at times because that's where the money for the winnings comes from.

In this case, it depends how you view those games that you get that you didn't want. Returning them to GOG isn't exactly a given and it's rather risky trying to trade them with other players. Many of whom have the game anyways.

It's just a really crappy way to set up a promo, especially given that some of these games have been discounted more in the past and will again in the future.
Are you seriously suggesting that something not being enforced makes it legal? This whole business is built on the fact that a lack of enforcement is not the same thing as being legal. Otherwise, we would all be going to abandonware site rather than wasting money here.
There's no false advertising because they provide very little information. Random can be fun, but there are better ways of doing random that would be less exploitive.

True doubles seem to be extremely rare. Lots of doubles turned out to be piñatas bought as gifts (no need to check your library, since a gift is a gift and not for you anyway) and people who owned everything except Dreamfall and/or Republique (sold out).

The usual 30 days withdrawal right applies (6.7d of GOG user agreement)

Why? You have the right to withdrawal from every purchase. The only case where they should mention anything is, when there is something where you DON'T have your usual rights.

Really? I actually thought that you have that right (usually) and they must tell you about your rights and the time period actually only starts from the moment on they tell you your rights.

Anyway I'm confused now. I would like to hear from someone who actually did that and ask for a withdrawal and got away with it.

GOG tells you everything about your rights all the time. You register here? You agree to the user agreement. GOG changes the user agreement? They tell us about it (they even told us BEFORE they changed it). You put something in your cart and go to the checkout page? Look at the paragraph below your order: Note: I copied this from a checkout page where I only have 1 piñata in my cart (nothing else). It still says "This purchase will be subject to consumer withdrawal rights, which will end once the digital content is downloaded." - as it does always.

No, I don't see any reason why GOG should mention that piñatas can be refunded too. They're just a normal purchase, just as every other game. And to be honest, I was even a bit surprised that GOG allows us to get refunds for piñatas. This turns this sale into a "Pick any game for 3 bucks" sale, where you have to buy 25 piñatas to get every game and ask for refunds of those you don't like (lots of wasted time for customers and GOG).

I've seen quite a few users saying they got refunds/store credit. I think it was in the piñata news thread and/or in the tracker thread. I'm too lazy to search though :P

It's astonishing how different experiences with GOG support can be. Mine have always been very positive. And they stay very positive. Wrote a mail about 3 hours ago, because Sword of the Stars: The Pit Gold Edition was added to my account despite the fact that I already own the base game and all the DLCs and asked for either a refund in store credit or a change to a gift code. They answered within 2 hours and I already have the store credit in my account.

Seriously? I wrote on Friday afternoon and I still don't have a reply. Maybe I chose the wrong option. What did you choose?

That's more due to the crappy system on gog. :P
If you have the base game with all dlc's maybe the gold edition should just be in your library.

Contact Us => My orders, payments and downloading games => order change (from regular to gift order)

I also gave them the important infos (order number and last four digits of my credit card) right away to make things easier for them.