What about a futures market that offers non-voting shares in startups (or Vegas-style wagers)? Startups relevant to the traded instruments can accrue some percentage of the option price. This gives you predictive power and funding. There must be some major pitfalls that I can think of, other than startups deliberately going belly up to cash out negative wagers :) One aspect of Ycombinator is, I guess, that of a prediction market with people trading in early attention and uptake.