Ultimately it's an entry in a SQL database. Removing a line and adding a line, or changing the ID of the owner is all it would really take. If it's coupled with some type of receipt in the system (rather than currently owned games) it might need an extra step.

As for gog to facilitate trades... Other than some type of verifying that the person actually has the game in the first place and a few checks/steps. I'd assume you could only 'give' a game. Though if there was some type of confirmation the game is locked and waiting some.. automated email then that might facilitate online transactions.

Perhaps transferring 1:1 wallet to wallet transactions (between users) in exchange for xyz game; That would be quite safe probably as long as both sides say they agree on trading the games. That would keep scammers promising a new game, but never actually giving the game after getting the money.

Hmmm... An arbitrary rule of you can't trade a game under a month old. This would keep you from say using a stolen credit card, purchasing a game, then immediately selling it (though such a slow process it wouldn't be very profitable doing that vs in bulk and as keys)

Thx for the information. It seems it all could work, and if GOG does go through with it I wish them the best and for their continued success.

Well likely fewer than 3% of the community would use the system if implemented. I can see it being used more to sell games under cost just to get rid of them. (I was unhappy very quickly with how crappy the lego games feel, and would sell them and a handful of others in a heartbeat, but it wouldn't be like i'd make a profit, in reality GoG made far more for the original sale than i'd sell it for).

In the end, if it's put in place it's going to be a far lesser deal than making noise about it. I expect it to make nearly 0 effect on the end goal of Steam or GoG.