I'm familiar with the prisoner's dilemma.  While game theorists firmly believed that the prisoners would betray each other, are you aware that experiments have shown that actual humans have a natural tendency to act more in cooperation than pure logical self-interest would dictate?  It's in our genes to cooperate.  I believe many Bitcoin holders will be willing to sacrifice some short-term gain in order to help insure the success of the project.

This is demonstrated by Ron Paul's ability to raise many millions of dollars, even though there is no direct benefit to the donors.  It's purely a matter of people cooperating to achieve a common goal.