Appropriate Response to Giveaway abuse.

Winner has 7 days to activate. You can't be sure he is regifting - maybe giving away a copy he already had.

Well as stated by @jatan11t it is 7 days. That is the time limit for support to get involved or any reporting actions can be done. Not to say you are not right and that person did in fact use the key to regift it. If you want your transaction to be honored as per site rules, you will need to follow certain guidelines as stated here, http://www.steamgifts.com/about/guidelines

edit* So if you are asking what we think you should do, we all think you should follow the same guidelines that keep us all in check.

I'd say report him right away, everyone is right in this thread and the winner does have 7 days to activate it but i can assure you it'll take longer for the ticket to be handled anyway so you might as well create a ticket now and close it if the guy does end up activating the game before 7 days have passed.

Improbable things do happen. A few days ago I won the same game twice in a row here, and a few months ago I won the same game here and on Gameminer. On the same day.

Still, I agree this is quite unlikely and is much more probably breaking the rules.

Tbh, i wouldn't do that (no offence to P4INKILL3R).
Even if it takes time, he'll get into problems all the same if he doesn't activate the game for himself and if you explain the situation to support thoroughly after the 7-day period. He should not even get any CV anyway for that GA or even get suspended - which proven guilty would be the most deserving punishment imo - and the game does get to someone who wants it anyway.
Not worth putting yourself in danger just to endanger him more (as it's even probably unnecessary).

Just think of it like this (imo):

1. Assuming you don't do that:
   • 1-A) If he's regifting the game he won from you and he doesn't get another copy to activate, he won't have one to activate, therefore point proven to support. You win, he loses.
   • 1-B) If he's regifting the game he won from you but buys a second copy, it's irrelevant. It's like buying one before - i'd just keep a low key so he wouldn't catch wind of this thread, so he doesn't go and get one out of fear, just for sake of knowing that if he did pull this stunt once and backs down merely because of this thread, he'll probably pull it off again if he feels he's in the clear. You win and nobody loses.
2. If you do activate it / give it to somene else before the 7-day period:
   • 2-A) If he for some reason, as unlikely as it is for me, is gifting a copy he himself bought and you activate the one you gifted him, he's gonna be able to gift his own to the other user, but will report you for not getting his and rightfully so and you'll be the only one with your pants down. He wins, you lose.
   • 2-B) Trickier one of all hipothesis... If he's regifting but finds out the one he gave away was already activated and out of panic but also cleverness, goes and buys one ASAP and gifts it, again, you're still the one with the pants down. He wins again, you lose.

Unless i'm missing something, ofc, which anyone should feel free to point out. Can't see any other scenario.
So as everyone above stated, as annoying as it is, i'd wait it out as per the rules.