Felix Salmon sums up the whole thing in one neat sentence:

the government here seems to be coming up with ever-more-obscure forms of capital which it can inject into the banks.

It seems to me that all the seemingly inexplicable twists and turns of the banking bailouts can be reduced to this one sentence.  For the next round, I'm proposing a new instrument to be known as the "Squibble", which will have an unknown and unknowable face value based on a secret random numbers table, a payout schedule to be determined by spinning a big wheel installed in the company's headquarter lobby for that purpose, and a structure to be arbitrated under the financial laws of a country picked at random every quarter.  This will prevent anyone from definitely stating that the banks are undercapitalized.  It will also provide financial journalists with some much-needed entertainement.