A bicycle theft victim in Menlo Park, California saw her bike for sale on Craigslist. She notified the local police and, amazingly, the cops arranged a sting operation and arrested the alleged bike thief!
The police recovered another bike that was also reported as missing, so it really does help in some cities to report those bike thefts and save those serial numbers. I have photos of my bike bottom brackets where the serial numbers are inscribed in case I ever need to report a stolen bicycle.
Props to Ellen Fletcher, Dan, and others for the news.