Except that that aggregated data frequently aggregate useless info into a very reductive score. If I go to a $ restaurant, I don't value a poor review which bases itself on poor service. If I'm paying $10 a plate, I can handle almost any level of service if the food is good.

It's a sliding scale though, at $$$$ I would rate the service related review more highly.

I would LOVE if yelp let people rate reviews, as well as restaurants. Useful reviews deserver more weight than ones that say, "I hated it, and didn't leave a tip because the waiter was ..."