This whole housing issue is a freaking mess and I have mixed feelings about the squatters. While I do not believe they have "a right to housing", provided they don't wreck the houses, it is a better thing that the dwellings are occupied.
The banks don't appear to want to clear their books of these foreclosed properties for various reasons, I'm not sure there's enough of a buying market right now, and there's a glut of new housing, too.
Somebody smarter than I should parse what I just wrote; tell me where I'm wrong (other than the obvious -- that's it is stealing).