I was on the University of Penn's main campus leaving a Saturday class I teach when I saw an altercation occur at a bike rack on campus. The gist of it is that a student was unlocking his bike, when another student approached with a police officer. The approaching student had told the police officer that someone was trying to steal his bike, and that he couldn't find his bike key. None of this, as it turned out later was true. So, the actual owner of the bike was quite surprised to be accosted by the police officer. It got quite loud for a few minutes, and I kept my distance, but was watching to see how it was resolved. It took a few minutes before the offending student (the one who appeared with the police officer) realized his cover was blown, and he then darted across traffic and around the corner not to be seen again. That was a pretty brazen attempt at bike theft , and it reminded me of the importance of having some identifying information on the bike that others couldn't possibly know about. It turns out this kid had his name and phone number engraved on the handlebar under the tape. He said it took him a few minutes to remember it was there when the incident first started to unfold.
So, I'm going over my fleet in the next few days to make sure that I can ID them all. Of course I already carry the serial numbers of all of them on my cell phone.