Much has been said about Problems for GM with UAW and Bondholders
But dealer contracts are another issue, and likely cause for going the bankruptcy route.
Pontiac Headed for Junk Yard - WSJ.com:
"GM's last automotive division to be eliminated was Oldsmobile in 2000. That decision cost GM billions of dollars in dealer-buyout costs, led to messy litigation and frayed many relationships with dealers and buyers."