I was introduced to Yelp through the Infopeople online eBranch workshop. My first thoughts were, gee, yet another online review site. There are so many these days, from the big old-time players (AOL and it's Digital Cities) to fly-by-nights.
In looking through it however I realized that word of mouth is really working in Yelp's case. I compared a couple of local restaurants in Yelp and Yahoo local. The most recent Yahoo review was from over a year ago. Yelp's was from just last month. Yelp also seemed to cover many more local places than Yahoo local.
By the way, Digital City has no entries for my city (Davis, California).
Interestingly some "hardware" companies are trying to get into the local recommendation market. There was a big four page ad in a recent home decorating magazine for Philips (makers of audio, television equipment and light bulbs) for Philips Simply Concierge service. A free service through September 2007 (after which I'm assuming they will charge if it lasts that long) allows users to get a listing of restaurants, shopping, entertainment and other locations in any of 20 popular US cities sent to their cell phone. This is a service that would not interest me.