Bitcoins could be embedded in the game. The players would start out getting very small sums as actual in-game rewards, so it'd look like just a regular in-game

Bitcoins could be embedded in the game. The players would start out getting very small sums as actual in-game rewards, so it'd look like just a regular in-game currency at first. Then later they'd notice that a much bigger sum of bitcoins (say, 3$ worth instead of 0.1 cents worth) can buy more game content, and they'd be nudged towards out-of-game means for getting them.