Man pans bookstore on Yelp. Bookstore owner tracks him down, writes harassing emails, and tries to break into his house. Man responds by calling police--and Yelping about the entire experience.
In what can only be described as a paradigm of Internet justice, a California Yelp user named "Sean C." was able to follow up his initial negative review of a San Fransisco bookstore with this gem:
The user created a Flickr set of screenshots  containing threatening message that the bookstore owner had sent. Only once he produced the screenshots did a Yelp administrator offer to help Sean C. stop the harassment, according  to Gawker.
As Gawker notes, the store owner's swings between plaintive hurt ("I have no money to pay for help") and outright fury ("Do you not have a girlfriend... I can see why") are perhaps unique to that unique brand of Internet passive aggression that allows for brutal, anonymous honesty.
The bookstore owner was arrested and placed in psychiatric holding, and has been served with a restraining order, according to Sean C.