Most of the times, yes, likely accompanied by a sale for said game. Though if GOG for whatever reason are required to take a game down NOW (especially on a weekend, when most of the staff are gone), there's no notice.

Most of the games that have been removed so far have come back later though (and I think only about a handful have been removed at all, including those that came back).

Even on removal from sale, the games are still available for download for those that bought them.

There are currently 8 removed games from GOG.com. GOGWiki is your friend, be sure to update any pages you think need updating :)

second sight was on my wishlist and disappeared from catalogue with only a day's notice on the second sight forum (which I was of course not following).

Sometimes it sucks, what can I say.

I didn't follow Second Sight's forum either, but I was informed for that through the general forum. Thread here.

My bad. I did not look at the forums at the time, hence the confussion. Still, while I understand the reasons behind it a day's notice is not so great.

Also, I think the OP would be interested to know that removed games you already bought are (usually?) still available here on your shelf. I at lest can still download space rangers 1&2

Actually, as SimonG will be more than happy to tell you, once you get a notice to pull the game from the store, you have to pull it immediately, so a day's notice is usually more than expected. That doesn't cover cases like "Rights to sell it will expire on 31/12/2013, so get it while you can", but it's mostly for the unexpected ones. Yes, this is usually the case, and the few times that a game wasn't available, it was a glitch that was fixed within a few days (Chessmaster 9000 had that glitch, but should be fixed now).

Yes, as I said I understand the reasons involved. Both that, and GOG not wanting to warn us that they might remove a game from catalogue before the official notice since it would look like a scare marketing tactic should that notice not arrive.

It doesn't make it suck any less for that, though.