Yelp covers a lot of business categories beyond restaurants, but I think restaurants account for a lot of the site's activity. Yelp is a national (now international) site, so you get comments from travelers, which is not a bad thing. Yelp also definitely skews toward a younger crowd, and emphasizes its social networking aspects, but that's what keeps it fresh and energetic...and some of the folks actually write really well.
It's easy to search for a restaurant if you know its name, and Yelp does a decent job showing other restaurants nearby (like Urbanspoon, they're hoping people use it from cellphones to see what's nearby). It's also fun to find a reviewer you like and see what else they think. It's a bit difficult to browse for restaurants in Yelp, though. If you ask for restaurants in Columbia, you get over 400 listings from all over the area. Ask for Ellicott City and you'll get nearly 400, nearly all overlapping with the Columbia list. You can use filters to narrow things down from there, but it's a little cumbersome.
The ranking system appears to be a combination of the number of ratings and number of stars. For example, Pub Dog comes up as the number one restaurant in Columbia, even though it averages 4 out of 5 stars. I found a more than a dozen other restaurants with 4-1/2 or 5 stars, but they had fewer total (or recent) ratings. I couldn't find a good explanation of Yelp's ranking system, so it seems a little suspect to me. There are no links to other published reviews or blogs, so you have to rely on the credibility of Yelp's reviewers. If there are enough of them, that's fine, but when there are only a couple of reviews, you have room for doubt.
Best features: Active community of reviewers, decent depth and freshness of reviews, comprehensive coverage of area, easy to add information/restaurants
Room for improvement: Hard to search/compare whole county at once, doubts about the ranking system, wish there were more ways to filter or compare restaurants
Who do you trust when it comes to restaurant reviews? Who does the best job of covering Howard County restaurants? I hope my blog is a help, but there are certainly lots of other resources available on the web. This is one of a series of Restaurant Review Site postings that aim to find which are really the most reliable when it comes to local coverage.