[unlimited_power]

I encourage people to look at the paper Transactions as Proof-of-Stake & The End of Mining[0] defining a form of the idea. BitShares[1] (due out in Q2 2014) will implement this.

[0] https://bitsharestalk.org/index.php?topic=1138.0

[1] https://www.youtube.com/watch?v=5BV55IrZi7g