The Fed has been printing money to buy bad assets. Everyone is happy with this trade as the banks can't get rid of this crap fast enough.

However, when the Fed wants to get the money back they have to find someone to sell the bad assets to so that they can extract money from the system and cancel it.

Nobody is going to want to buy this crap back so the Fed is stuck with it. The money is out there and there is no getting it back. The very best they can do is sell these assets back into the market at a massive loss (this will even apply to Treasuries if yields continue to rise) so they can not get back all the money they pushed out there.

If I'm missing something then please enlighten me...