chrisv1963 - 5:47 am on Oct 3, 2011 (gmt 0)

The small sites (1000 url) are not penalized, although they usually have a lot of ads, high bounce rate and bad design... the keywords ranking remains the same. Maybe we should observe them carefully

This is correct.

My best big site with a lot of good content got pandalized.
One of my small and very crappy sites gained a lot of traffic since Panda (and again with the September 27th update).

My conclusion is that Google lost control over the serps. The algo got so messed up that they no longer know what is happening.