> Zagat employs people to actively review restaurants. That's fine for people who have the same taste as Zagat, but it's only one filter and arguably not very scalable.

It's not like there's one person per city, Zagat uses input from tons of people. It's also consistent, you don't have to wonder if the glowing review was written by the owner like you do on Yelp. Zagat gets people to pay for access to their reviews, that in itself should tell you something. Even better, Google will surely make them free, likely with some innovative tie-ins with Maps and Places.