I lived in a town that required all bikes to be registered and licensed, and all sales of bikes to go through the local government. It was such a big pain that I would rather just live with the higher risk of theft and the lack of enforcement.
The LAPD was ticketing riders on large group rides a while back for not having their bikes registered. It was a misapplication of the law, since the law was supposed to protect cyclists from theft, not get them ticketed if they didn't have their stamp. The idea was that the bike shop registered your bike when you purchased it.
The cyclists stormed city hall and complained loudly, and the police were forced to stop doing this.
