As a small business owner who could find himself on Yelp, I can somewhat sympathize with some of the owners (although not the woman in the article, she just seemed nuts. A much more appropriate thing would be to contact the negative reviewers and try to learn how to make her store better).

The problem with Yelp is probably the search rankings. Chances are, Yelp has higher PageRank than some local company, and when someone search for "company name" on Google and Yelp reviews come up, it could harm their reputation.

While most people haven't heard of Yelp, they could easily find unfair negative reviews of your company easily.