The first thing I do when I buy a new bike is photograph it, and flip it over and photograph the serial number (usually, on the bottom of the bottom bracket housing). I've had a bike stolen before, but still, I highly doubt my efforts would do any good for theft recovery. Makes me feel less powerless, I suppose.
My local police department offers bike registration every year here at Bike to Work Day. Again, it's theft recovery, and not law enforcement for vehicular biking.