They basically made a "craigslist:all" search engine for bikes. This helps you find your bike if someone is trying to sell it on craigslist in another city.

Then, they wrote a blog article filled with hyperbole about business theory, angry NPR readers, Pee Wee Herman, and photos of flying sparks.

Primarily community driven to raise red flags about stolen bikes. That said, it's pretty easy to look at an advertisement for a bike and know if the seller actually knows anything about it.

Hmmm, now that you mention it, that'd make a great crowdsourced feature for CL or LoveRack... a flag button for "looks stolen."

2 ideas: 1. stolen bike finder button should stand out a bit more. maybe in red (btn-danger) 2. Dont have a stolen bike but is there a way to flag listings so that other browsers know they are browsing a stolen bike. Might auth with a social network and require a couple friends to flag it as well (so individuals dont do it maliciously). But would massively improve your data and would help the community self police.

How would people identify stolen bikes that are not their own?

I've seen suspicious craigslist ads in the past.

Many bikes photographed in the same spot. Poor-quality photographs (blurry, etc.) that make it difficult to pick out distinguishing marks. Very little detail about the bike's components.

None of these are proof of a stolen bike, but each is a useful flag, an indicator that the ad is worth further scrutiny, and flagging could help people looking for their bike.

My thought was - recruit your friends to flag it with you. When things get stolen you normally tell your friends, who tend to be sympathetic. Better than no flagging, though I admit this can be gamed quite easily of not policed well (one set of users flagging several bikes could be of concern for example)