Sis bought a Subaru that was sold new in Boulder, CO... was imported into Canada and was up there a while, came back into the states and was somewhere (that I can't recall) for a while, and then found its way to Chicago, all with the same owner who bought it new. So it was a one owner car that had been with an owner who had lived in different places.
If nothing else, the CarFax was interesting documentation (the dealer provided one for free). It really wasn't necessary, since the body of the car really didn't hold any secrets, outside of a hood repaint, and all of the repair receipts were in the glove box.
I will go out of my way to get one if something doesn't seem right about the vehicle, otherwise, I won't bother.