My church does background checks on everyone in leadership and everyone who wants to work with kids, and a routine investigation turned up a hit for me in Arizona for a dismissed charge of "possession of drug paraphenalia" in 2003. I haven't been to Arizona in a long time, and I've never been charged anywhere for anything, so I was concerned that I was a victim of identity theft of some sort. I thought it most likely that someone made up a fake social security number and it randomly matched mine. However, when I looked at the report, I saw that it was probably legitimate: same birthday as me, same first and last names, no SSN given, different middle name. So it isn't a fraudulent record, it just isn't about me. I don't think I need to follow it up any further, and there probably isn't anything I can do anyway, if it's real.
Nevertheless, here's a link Molly passed along that may be helpful to anyone who needs to take back their identity. California appears to have some very strong laws that work in favor of the victim, but you've still got to do an awful lot of legwork yourself and call a bunch of places. It looks very tedious and frustrating, and I hope it never happens to me.