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Sounds like something that can't be done since for example won Overcast - Walden and the Werewolf but user who made giveaway hasn't been on for about 5 days so not sure if its legit and even added him. But if they did create that then I wouldn't be able to try and win the game again and a lot of the really good games like Crew and Evolve often have people giving beta keys even though they aren't suppose to do that so that would block access to legit giveaways after winning fake one. But then again you could reopen chance to join giveaway after the 1 week after marking unrecieved so I could see it work.

even though your suggestion may prevent regifting, I don't think that feature should be implemented, well... for example... imagine that I win a giveaway for GTA V, I activate it and play it, then I become to love it and think that I should share this joy to our community, so I buy another copy but I'm not allowed to make a giveaway because I win that game before... it's anti-fun...
your suggestion is good, but it may not work for all cases, just saying

Not activating win, and abusing giveaway feedback, are both against the rules in the first place.

Regifting is only one of the possible follow-up events to those two offences.

Fix the root causes, not the symptoms.