It's ironic isn't it - for an animal that suffers from one of the lowest libidos in the world, Google's panda sure has manged to f**k a lot of people at the same time!
I personally agree that it's a number of factors having influence - ad blocks, thin content, scraped content, daisy cutter pages, keyword stuffing etc. Google say it took them over a year to construct and I think they've gone for the 'shock and awe' technique. I really feel for any quality white hatters out there (which I'm not) that got hit. At least I know what I'm doing wrong, many others can't comprehend their slap.