The information comes from Lexis-Nexus (sp?). I ordered a report from them last year. They had addresses that I had forgotten about they were long enough ago. (I'm a lot more than 20 y.o.). They even had info on current occupants names & phone for people living there now. There was past employment, relatives and associates (friends). Kind of scary the info they had but I guess that's how CA's track you down if you stop paying and move around!!
Starting Score: 500's
Remember also, that census reports are all public knowledge as well. You can find stuff if you dig deep enough in the public libraries. It's not eery though.