actually - this "user-knowledge" idea is rather intriguing.
I agree, y'all have pointed out the biggest flaws of it - it could easily become readily abused by others . . .
perhaps instead, we could impliment some sort of test or quiz, where the final score we obtain gives us a ranking on a 1-10 scale. Perhaps also we could have it where after 30 days, you can retake the test - just in case you recieved a low score, so that way it's not permanent, either.