Yelp, one of the most popular Web sites that let people post opinions about restaurants, shops and local services, is being sued by several small businesses that claim they’ve been pressured to advertise on the site in exchange for getting negative reviews squashed.

Yelp denies the claims, but exactly what happened may never be clear. And regardless of what happens in court, the lawsuits could taint Yelp’s reputation as a leader in online reviews.