Yeah, I have to say I can't stand when people do that to any vehicle. The wrong backspacing can add a lot of extra stress to ball joints and steering components, and in a number of places you can get written by LEO for having the tires sticking out that far, kicking up rocks to everyone behind you.
IMO, its usually people buying the wrong rims (off Craigslist) and just slapping them on their rig.
SMB-less as of 02/04/2012. Our savings account is richer, but our adventures are poorer.