What happens to a community review site when members of the community use it as a weapon against people they don't approve of? Sites like Yelp and Citysearch are finding out, as users target businesses that supported California's Proposition 8 (the state's recently-enacted gay marriage ban). The results so far are not pretty. They illustrate some of the weaknesses of online reviews, and the complexities of managing a community site.
It's a learning opportunity for any company that relies on online reviews or runs a website that allows user comments. I wrote about it over on the Rubicon site (link).