I agree reputation isn't an easy problem to solve. I think taken to its logical limit something like what you've described above is likely close to if not the

I agree reputation isn't an easy problem to solve. I think taken to its logical limit something like what you've described above is likely close to if not the correct solution. Using the tried and true methods that already exist in the public key infrastructure of the web, I think the problem of tracking reputation online (in a reliable way) is something that will be solved in our lifetimes.