This is taken from a Washington Post article…

Car valuations matter because an increasing number of consumers are “upside down” on their auto loans, meaning they owe more than the car is worth. In the first quarter of 2007, 29 percent of consumers were upside down on their vehicles, Kelley Blue Book reports. Additionally, on average, people traded in cars on which they still owed more than $3,600. And what do many of these buyers do with that loan balance when they want another car?

They roll that negative equity — the $3,600 and often much more — into yet another vehicle loan.

A lot of this insanity stems from the Big Three pushing their product. As the Washington Post article says in another place….

Increased pressure on automakers and dealerships to sell vehicles over the past few years has led to more car loans being made to riskier borrowers. Auto dealerships originated $50 billion in new-vehicle loans to subprime borrowers last year, according to retail data from the Power Information Network (PIN), a division of J.D. Power and Associates, a marketing research firm.

To make the loans work for many of these subprime borrowers, who typically have shaky credit, the lenders are offering longer payment periods. New car loans lasting more than five years in 2006 accounted for nearly 55 percent of loan originations, according to the Consumer Bankers Association.

Subprime vehicle buyers, those with credit scores below 650, have loans that last an average of 61 months, compared with 56 months for more creditworthy consumers, PIN found. Higher-risk buyers also tend to make lower down payments as a percentage of the purchase price, paying about 11.6 percent compared with 17.4 percent for other buyers.