The loan type with the biggest jump in defaults are the prime loans. As a percentage of total loans the default rate is still lower but since most loans are prime that translates into a lot of defaults.
The best line from this article: "Freddie Mac estimates that 40% of the loans they have in foreclosure are on vacant homes. The borrowers don’t want a modification. Home prices have fallen so far that they will not see any equity for decades. So why pay?