The last time we did a deposit bonus giveaway it was for Golden Tickets and in exactly the format you suggested and ran for 48hrs each time. Unfortunately, one individual started depositing and withdrawing the same 2 BTC constantly for 48hrs every time we ran it. We think this is a lot fairer on everyone and a lot less attractive for high rollers to abuse.


Edit: I forgot the happy ending. They spent a fortune in mining fees and didn't win the Lambo.