This seems like a cool idea. What I like about it is the way that it assigns a quantifiable value to mathematical proofs, and incentives their production.

Assuming proofs are valuable (which I believe they are), then by creating a market we can learn an approximation of what they are really worth to people.

Also I like that it is another outlet for mathematicians to profit from their skills. The options for pure math as a career are fairly bleek right now (fuck the nsa, academia maybe, not many research jobs in industry). I could see this market as a way to incentive more pure math research.