Barely a month ago, thousands of rioter pictures were funneled to the Vancouver police via Facebook, Twitter and the broader internet. The internet dragnet seemed novel at the time. But now the same sort of viral manhunt is underway in London.

The most visible effort is, a clearinghouse for online images of U.K. rioters. The website features a lengthy slideshow of pictures engaged in, close to, or seeming to reap illicit awards from the British violence, with each person in the picture marked with an identifying number or letter. Off to the side is a form soliciting the name and "further details of rioter, e.g. Facebook profile link, Twitter username, email, telephone number, etc." Zavilia accepts pictures via email, Facebook, and Twitter. The site promises to pass to the police information about subjects identified by at least several people. A site operator told TechCrunch Zavilia is run by an anonymous "team of UK citizens."

There are at least a few additional attempts at internet justice under way, including the Facebook page "name and shame the rioters" and a "London Riots Facial Recognition" Google group.

If history is any guide, this online manhunt could give police new problems to handle even as it helps them identify suspects. In Vancouver, a water polo player photographed stuffing a burning rag into a police car gas tank had to leave home after receiving threats of physical harm. Another rioter faced thousands of online hecklers after he posted an incriminating account of his actions; a Facebook group had been formed to shame him specifically.

It's also not yet clear how effective this sort of online activism will be at netting actual prosections; Vancouver authorities told the CBC in June that while they could handle the flood of evidence and the spike in investigations, it would be very expensive and time consuming to bring cases against 500 to 1,000 people.

But for frustrated Britons watching chunks of their country set ablaze, exercising even the most minute sort of power brings an outsized sort of psychological relief. And, handwringing about unintended consequences aside, exposing socially harmful behavior is among the more redeeming ways to use the internet. It certainly beats FarmVille and cat picture captions.

Update: And let's not forget the Catch a Looter Tumblr and the Metropolitan Police Flickr, via The Awl.

[Photo of rioting in Birmingham, England today via Getty]