Where is this thread going? Haha

It's been 10 years. This isn't something that just happened a month ago, in which case the OP would rightly be miffed about it. The statute of limitations is up. You've gotta move on with your life at some point.

As someone who did in fact win a prize this way on GOG as a contest participant, I can confirm that there has been at least one contest on the GOG forums where the participants received their prizes. The contest was to celebrate the arrival of Dorfromantik where the prizes were all key codes for the game. I attached a screen shot of my receipt, which mentions contest key.

It looks like the issues with prizes not being announced thus not given out have been in cases where there's been tangible items involved and not just key codes for free copies. Regardless of if it was Introversion Software that withheld the prizes or someone at GOG that raided them, it puts GOG in a difficult spot.

And then it happened again.

And then it happened again.

The last time was just last year. (I think there was more, but I can't be sure)

It's not just en embarrasing one time screw-up. How long it's been going on isn't a mitigating factor. If anything, it's the opposite.

I have been lucky to win two contests over the years, one where the prizes were GOG games, and one where it was a physical book. In both cases winners were announced on the forum.

I simply got busy with life...

I've won at least three.

One was for Disco Elysium (code sent direct to me via PM - GOG staff override as my PMs are off).
One was a comp for... Dead Synchronicty (I think). Prizes magically vanished (as somebody decided to tell winners on Twitter to "mail us at contest@gog.com" like an idiot). Only by banding with other winners and applying constant pressure did we get anything - in my case a mug that was nothing to do with the game and some $10 coupons.
And there was another I can't fully remember now - but yeah a full on vapourcomp and after some chasing I gave up.
I think i also won another one or two vapourcomps for codes that again got gobbled by randoms emailing the contest adress.

The root has primarily been incompetence here in these cases (even after they made some changes to how they did things).

Now I know why this hasn't annoyed me. I don't think I've ever entered such contests.
I prefer to buy my games. This guy explains it well:

https://www.youtube.com/watch?v=w_urWSSZgwU#t=38

Exactly. Something given has no value. You must buy it to really call it yours.

That makes a lot of sense, because game keys essentially are unlimited and can, if need be, be generated and paid for by GOG (minus profit margin so always less than retail), plus I doubt that GOG management has a shortage of game keys and therefore would not need to nick keys from GAs. If anything, to me, it seems like GOG isn't stingy with keys at all.
Physical items, OTOH, are in limited supply, cannot be spawned by GOG and also incur additional cost and labour for shipping and handling, plus would need to be paid at retail price if they can be procured at all.
I disagree. Some of my most appreciated belongings were given to me, plus if you received the item through a contest, you would of course have paid for it, namely by labour or IP, for actually making whatever entry you submitted. Seriously? This would take an imbecile or someone from before the internet era to even remotely believe this would be a viable way of doing those things. Now, honest idiots like myself would obviously never fraudulently claim a prize even in such an obvious invitation to abuse, but having used an email account for more than three weeks should have been proof enough that not all everyone is clinging to proper conduct, and therefore safeguards are required.

Abso-fuggin-lutely irrelevant.
We aren't talking about ownership.
We ARE talking about incompetance / cronyism / fake giveaways (the latter of which is entirely illegal in the EU - maybe Finland has some special pants-drunk laws on that?).

Somehow I knew this would become another one of those "everything is upvoted" threads.

I presume timppu was joking. I sincerly doubt he's unhinged enough to refrence Starship Troopers as a life lesson for real :D

Mate, I still hold grudges for guys who picked on me in primary school. A decade-old silence over a giveaway is chicken feed compared to that.

And I can report I won a giveaway sometime ago here for a Winter "write about your favourite winter-themed game" contest. I tend to believe MOST competitions here do indeed run to completion, but there's a few which are left in question.

What I can say about all of this is it's GOG's lack of transparency and/or communication with the forum which fosters distrust and a certain degree of anger. The vanishing giveaways are merely a symptom of this problem - had GOG come clean and explained to us that:
A. The competition was complete and all winners got their stuff, or
B. The competition was cancelled due to "reasons beyond GOG's control" (or whatever execu-speak they decided to use)

then the matter would have been settled, and users here would have little reason to doggedly pursue it for years.

An explanation. ANY explanation. That's what most of us want. NOT SILENCE.