This is one that I have been wanting to make for a long time, it's simple, fun and good returns!
In order for gambling to have good return for players, the house will have to lose! Beside, I don't see how adding a gambling service add much to the bitcoin economy.
Not everyone has a linear utility/BTC curve. In many cases 0BTC and .5BTC are very similar in value to someone and you are doing them a big favor by letting them risk their small amount for a big one. Good odds doesn't have to mean positive nominal BTC expected value. It just means good odds relative to other offerings.
