I think that, even in an altruistic community such as this, the money that goes with a great idea can stifle real collaboration. Fear of losing out comes into play. How then can there be clear, universally understood rules of engagement that say basically "here is how we create IP in this community."
One way would be to say that in an open forum like this no IP can be made as discussions are held in public. That is simple but has its (hopefully obvious) drawbacks.
This, I think is the single biggest mill around OpenIdeo's neck in terms of attracting talent from within corporations to the table. Hopefully I am wrong but I think that it needs clearing up - assuming that hasn't already been done and I just missed the memo.