Well he clearly stated this point :


Terms: If I don't receive any submits that are worthy/good enough for bitvest, then there may be no winners. Or only a minor consolation prize of .02 to .005 BTC if its
only minorly good. I have the right to determine which suggestions are unique and worthy of prize & which are not. For example suggesting implementing blackjack is a fairly common casino game,
and something I would most likely implement down the road, even though I implemented your suggestion, you wouldn't win in this case.

So this is not a scam or anything like this he was honest before people did participate!