When I lived in Utah, that information could be easily had by just going down to the MVD, giving the plate number, and paying $2.

Illustrative story:

A friend and I saw an extraordinarily cute girl walking around campus one day. Being complete and total retards, we didn't talk to her, but just tried to follow her around. We tried to see where she'd go, but eventually lost the trail. We went to the same place the next week to see if she'd turn up again, and sure enough, she did. This time, we followed her to where she got into a car and drove off. We wrote down the license plate number, went to the MVD, got her name number and address, and went home and called her. We pretended to be doing a survey for some psych class, but eventually let on that we had just thought she was cute and wanted to call. Oddly, she didn't seem to be very bothered by that.

We all became sort-of-friends, and she went on to date our roommate for a few months. It's only now, several years later, that I look back at this and realize how incredibly creepy we were and that other people go to jail for that kind of thing. That's Utah, the naïveté capital of the U.S.

Last I checked, Utah had changed their system since then so that you could opt out of the public availability of the info at the time of registration. Many other states had the information just as easily accessible, though.