GMAC's Recalcitrant Bondholders

Can someone explain what's going on with this GMAC tender offer?

The basics of the situation are clear: back on November 20, GMAC (which is 51% owned by Cerberus and 49% owned by GM) offered to swap existing bonds for new ones, as part of its bid to become a bank holding company. If the offers were taken up by 75% of bondholders, then GMAC would have enough regulatory capital to become a bank holding company and therefore eligible for TARP funds. But so far only 22% of bondholders have tendered, and despite today's announcement that GMAC is extending the deadline on the offer, it seems improbable that the 75% figure will be reached.

The bit I don't understand is this: why has the tender offer failed to gain traction? At first glance, the haircuts involved seem minimal -- in fact for most of the GMAC (as opposed to ResCap) bonds, you get an identical bond in return, plus a cash payment for your troubles.

Of course there must be a haircut somewhere, because simply swapping bonds for identical bonds doesn't raise your regulatory capital base. A haircut is not necessarily a bad thing for bondholders, since the viability of GMAC would increase were it to be able to tap the TARP, and their bonds are worth very little these days anyway. But it would be great to see an indication, somewhere, of the effective haircut that GMAC is asking its bondholders to take.

Because if GMAC's bondholders aren't even accepting a modest haircut, what are the chances that GM's bondholders will go along with the surely much larger haircut which seems to be embedded in the current bailout plan? If they're all really this recalcitrant, maybe bankruptcy is the only resort after all.