Aver: Some guy is selling GoG's gift codes for The Witcher 2 for just 24 dollars. They works perfectly (He has over hundred positive comments). I don't think that he wants to support TW2 and buys codes for a 50 dollars and sells them for a 24 dollars, so is it possible that you have dishonest employee or your servers was hacked?
Have you written to support about this? If not, please do so immediately. It's not certain that they will read this thread, and they really need to be informed of this. Be sure to give them as many details as possible, just don't post them here (to avoid tempting weak souls).
KavazovAngel: He either bought them or received them through a competition or something. So what's the big deal here?
More than a hundred codes? Doubtful. This sounds highly suspicious.