Instead, I wonder if YC can formalize & self-regulate a secondary market as an intermediate step before IPOs. This is already happening, but with undesirable side effects.
I agree this isn't something that is ready for primetime today - but it could be in the near future. Even multinational banks are now looking into using block chains for funds transfer.
Besides that, it's a beautiful solution to a 30-year-old unsolved problem in computer science (the byzantine general's problem).
In fact, it's much easier to steal someone's credit card details which get transferred around and stored all over the place and are embossed on a piece of plastic you carry with you in your wallet.
We just happen to have a grossly expensive and unfair insurance scheme on top of it that indemnifies consumers against their own stupidity and carelessness. In the future, such a scheme, if so desired, could certainly be added on top of Bitcoin or other blockchain technologies as well.