In other words, these "lenders" holding these mortgages as part of securitized mortgage bonds may find themselves in the same position as someone who buys a property only to find that the previous owner left it with some kind of fatal flaw (e.g., soil contamination) that effectively makes it worthless. Very often, the best course of action in that case is to try to negate the original transaction.
Add to what you said is that some title companies will not give a General Warrantee to a home that went through foreclosure because the risks involved with the title company having to payout in case the documents are wrong is too great. I just had a title company tell me they cannot give a warrantee on a property because it is muddled in foreclosure. Several national title companies last week joined in and said they will not give title warrantees for foreclosed properties until they can guarantee the paperwork will stand legal challenges.
Again, though, more chaos in the financial system that will eventually put several big banks on the brink.
If you ask me, I almost see financial collapse as an inevitable, but there is always the chance we pull through this if all the right pieces fall into place. This is one of them.