The folks who find themselves most upside down are relatively recent purchasers of 1/2 ton SUVs,and folks who purchased 3/4 and 1 ton Diesel pickups a couple of years ago.
The SUV buyers -Suburban/Tahoe- probably paid $38,000 on average,and financed well over $30,000.Used Suburbans have absolutely nosedived in resale value,so they are poison as a trade in vehicle.These poor folks won't be rightside up until about 5 minutes before their last payment. Many of them bought before it became obvious-say 1 year ago-that gasoline was heading one way-up-for a long time.

If these owners are middle-middle class they are looking for a way to bail out of the high fuel costs, but they are stuck until the end of their loan.

The Diesel pickup buyers aren't in quite as bad shape,since someone will buy them as a work trucks-eventually.Unfortunately, many folks bought big diesel pickups as "fun" trucks with the idea that"they get good mpg because they are diesels".Diesel pickups were "hot sellers" until about 1 year ago,so they weren't discounted much-averaging about $40,000 for a loaded GM or Ford-Dodge was cheaper.
Charlie