Robert_Charlton - 8:28 am on Jan 8, 2012 (gmt 0)
I think the search engines tend to look only at bounces that go back to the SERP within a handful of seconds and then make another choice from the same result set. That is sometimes called a "fast click". And even then, we still have a relatively noisy signal.
For certain kinds of non-SEO research, I will often go down a serps page looking at several results. These in fact aren't pages I dislike... they're just the ones that initially attracted me the most... and going back to the serps can mean that I'm following up leads and learning as I go. Perhaps I've even picked up enough additional information to refine my search further.
But this isn't necessarily a problem with the pages... it can reflect the limitations of my knowledge when I started the search
I'm a little concerned when I see the "do you want to block all results from example.com" message when I do this. Makes me worry that I might be hurting perfectly good sites. I assume that Google is aware just how noisy this signal can be for certain searches, but one never knows.