I just had a similar problem. I played the daily Challenge game, and I beat the challenge and it said I won a Steam Key. I assumed it was going to be some cheaper 2D style game or something, and I was fine with that. It was free after all. When I went to enter the Steam Key that they sent to my email address it said it was a duplicate key and that another Steam account had already redeemed it. I sent an email to the support account just now, so I'll give it more time for them to respond. I even told them that it was a freebie, and they don't have to do anything for my situation, like I'm not out anything, but I will hold off on putting my credit card information in on the site or downloading anything from here until I at least find out that the site is legitimate and see how they handle this. The moderator seems to be pretty responsive, so I consider that a good sign. We'll see though.