This is actually a great concept and deserves more attention.
It's so simple yet has no much potential.
There are flaws though with trust... As you could essentially bid up every game for as long as you don't exceed how many Bitcoins you own. If that ends up happening there'd be a high chance you wouldn't pay out. But yeh.
I'm glad you like the concept!
One of the things we can do to mitigate the risk for users, is to put up a relatively large collateral with a trusted member of the forum here. So that if we were to ever disappear or run off, (which we have no intention of doing), the collateral could be split up between members who lost money to us, and we would lose all of the money we gave the trusted member.
If people are not playing because of a lack of trust in our site, we will do it. The main reason we haven't yet, is that the members on the forum who are advertising escrow type services, charge 1% or more to hold your funds.
For your particular attack, one way that you might discover we are doing it, would be the fact nobody "known" would ever seem to win. Since we would win every game until we went bust/disappeared. The one major attack I think people should be concerned about, is if we just wait for a big game to happen, and clear out both players and disappear.