I just got done reviewing all my sites - about 20 - looking at data from January 1, 2011 to today.
The only sites which didn't get Pandalized had thicker content. The thin ones which had some pages with one line got nailed; whereas the sites with a paragraph or two, or three or more, survived.
I'm pretty convinced size is a significant issue. Not the only one, but it's clearly one.
Now the question is whether just because anorexic pages can get you Pandalized whether adding meat will get you un-Pandalized.
If memory serves, I think it was Google employee John Mueller in the Google Support forum who told one webmaster adding a few lines would help deal with Panda, but it sounds as if some webmasters here have already tried this approach without success.
In any case I might try it myself - at least on a few sites - just to see what happens.
[edited by: potentialgeek at 7:21 pm (utc) on Jun 30, 2011]