Negativity?

Well written post and good info as always, but are you sure that GTA V is a VAC protected game? From what I've heard the online version of the game doesn't run on VAC servers, and GTA V isn't to be found in this list:
http://store.steampowered.com/search/?category2=8

I've never played the online version of the game, so I'm not 100% sure.

If it's not VAC protected, gifting of the game would work as any other non VAC game, no restrictions, right?

Good points. At any rate, the situation one year ago wasn't so bad as it is today - people feel the obligation to tell others and confidently declare "FAKE!" on giveaways, and I've seen some people take it up to a point where they'll say "It's okay if I get suspended as long as others can see this is a fake"

The "stupid" or so reason is maybe the fact that R* is pushing their Social Club as another uPlay, and hence they absolutely don't want to increase steam sales because they only get 70%, whereas by physical and digital purchases on other sites they can get 100% of their value. This is a conjecture however, I've no idea why they do what they do.

So very well said, and much nicer than I would have said it. ;)

there is no GTA V Gift in your inventory. why you lie ?

I don't blaim the community for it, I do realise and understand that there have been a lot of fake giveaways in the past hehe so no worries man.

Thank you hehe

I will change the content of my channel soon to be more varied.

He has the three GTA V copies in his inventory now, so at least that part is covered.

Thanks m8 I will do that :)

Take screen shots of all means of how you tried to contact the winner and provide to support with a request to re-roll 7 days after the giveaway ended

Giveaway creators have 1 week to send the games after the GA has ended and so do the winners to activate their games and mark them received. If this means another week or the same week the creator has to send them is kind of open to debate. I completely understand that you want to get this out of the way after the Steam Gifts Community has shown you their best side but now that 2 out of 3 copies have been delivered I highly doubt anybody is going to rush you or make any more unfounded accusations.

So for now just wait ;)

Check if he was even online in the meantime; many people log onto the site maybe once a week.
Also, use Sgtools.info to see if the winner has a past of not activating a won gift; it can be an indicator that dear winner likes to run away with the key and resell it. ROW GTA V Steam gift copies are especially valuable, you can easily get at least 30 USD for it (which many not seem much, but for example, it is almost a day's salary for me, almost a week's for some others). This is especially likely for level 0 AAA public giveaways, since level 0 and 1 are the most infested with autojoin script/bot users and resellers who would gladly take a few-day suspension for anything over 5 dollars of profit.
Keep in mind that winner has a week to press the Received button after you delivered the gift.

If a week passes with no response, make screenshots of contact attempts, then ask for a reroll with a reason of winner not responding, and attach the screenshots in the first ticket description. (Also make sure to cancel the gifting process before you send the ticket out, in case the original winner takes it.)

If you want to use giveaways for self-promotion, sadly this is the kind of behaviour you need to get used to. It is annoying, but not insufferably so. It takes time, but you can learn how to deal with the user base of this site and how to adjust giveaway restrictions (or the lack of) for different SG demographics.
Although I have to add: people stealing Steam gifts are rare. If he does take your copy without marking as received, it is easy to send for a Request Received feedback ticket with easy evidence. Steam gifts and gift links are the most difficult to steal for reselling without getting hit by an inactivation mark and suspension.

Also, keep in mind that since your giveaway was, to say mildly, suspicious as all hell when you originally posted it, many users most likely entered to keep an eye on it to see if it is legit or not. He may be among those, although in that case a simple message of "yeah, please reroll" wouldn't be too hard to write.