Road a Sears Free Spirit when I lived in Seattle, and never had it stolen even though I just kept it locked up with a cable lock downtown. On the other hand when I lived in Savannah my Western Flyer got stolen. Some people are just more desperate than others.

As for professional theives, I think you will find them in every large city. Here in Austin I witnessed some pros -guy jumped out of a pickup snapped through a lock and tossed the bike in back before the owner could even make it out the front door. Even pros are opportunistic though, I'm sure the guy simply went for the bike with the weakest lock, but I think if you have an escape driver you're a pro.