It's like a Bitcoin Payday Advance loan.   I don't see anything wrong with charging high interest rates, as long as he's open and upfront about it.

1. Get 0.10 BTC loan
2. Buy 10 raffle tickets
3. Get your friends to do the same thing so the raffle ends faster
4. Win raffle
5. Pay back loan
6. Profit

Of course, a guy named Vinny might show up at your door and break your legs if 3-5 don't quite go your way.