Where does List Source get its data?

[Ed Taslak]

Has anyone wondered where List Source (and others) get their data? 

I go on all these county assessor sites and they all make me confirm that I am not using an algorithm to mine the data off their records. I'm guessing that as big as LS is, they would probably get caught using some advanced data mining algorithm. I'm sure some small guys can do it and perhaps get away with it. 

Can anyone shed some light on this? Where do they get the data from?