I don't think it's going to be one system but rather many systems. I think there are a host of online communities that have arisen in the last few years that are actually doing this. A good example is Stack Overflow/Careers 2.0. The fact that companies are hiring people on the basis of their Stack Overflow reputation graph should strike fear into the hearts of college administrators everywhere (but likely won't of course). The change won't happen overnight but we've come a long way in just the last few years in terms of mechanisms that could ultimately rival the university when it comes to signaling and I think this shift is only getting started.