[wpietri]

I suspect that's not particularly difficult to solve. Escrow is one solution. Profit sharing is another. Independent valuators would be a third. I imagine any energetic business lawyer could come up with a number of other approaches.

The problem is that nobody wants to buy raw ideas. Any decent entrepreneur has ideas coming out the wazoo. People who aren't decent entrepreneurs could probably use ideas, but they'll very rarely recognize that they need them.

There is a great market for proven ideas. That's why a major route for startup exit is acquisition. Once you've achieved product-market fit, plenty of people can see the value of your idea.