Buyer beware??? I find it interesting that the nay sayers don't offer up anything other than "I think..." Dear Lord, of course bad things can happen. So can bad things happen from buying from the dealer down the street, the want ads in the paper (they still exist???) or your neighbor down the street.
Bought our last F550 off an ad on ebay; ended up finding it listed locally, worked the phones for about 5 minutes and solidified the deal for less money. Flew down, looked, paid, and came home.
Chances of finding what I wanted....at home: nada to zero. (search 550, auto, 4x and air suspension and let me know how you do).
Purchased a Peterbilt off ebay a couple years ago too.. The net works (you all tend to trust this forum...so what's the difference?).
Trust but verify...in everything. It's a great medium (ebay, etc) for locating what you want.