When you kill monsters do you get satoshis? People would LOVE the idea of looting real spendable money off of mobs even it was only 100th of a penny each time.
Marx you should take this into consideration. Take a very small percent of the profit you make in Bitcoins (or fork some over yourself to get it started) and make it so that each mob drops a few satoshi's. Players can then either cash out the satoshi's after they collect a lot (1 mBTC for instance) or they can re-use the satoshi's to buy stuff in your in-game store.
wow, it would be gorgeous! If i found a tibia like game in which the monsters drop satoshis I would be playing nonstop till addiction!
An idea would be charging an yearly (or monthly) fee from players to fund those poor monsters