In the bubble mania days, many corners were cut and people are discovering many violations of Truth In Lending Act (TILA). It seems that can be used as a pretty powerful weapon against the foreclosure juggernaut.

see http://bigpicture.typepad.com/comments/2007/08/coming-soon-tru.html

TILA violations can cause some mortgages to become unsecured.

Judgments can render a whole class of CMOs worthless.