I found a post that actually offered some interesting insight about this. It specifically talked about this update impacting the yellowpages sites. You can read the whole thing here:
http://www.localseoguide.com/its-mayday-for-yellow-pages-sites/
The main commentary out of it all was this:
While we are testing various hypotheses on some sites, based on what I have seen thus far, sites that have a lot of URLs (e.g. tens of millions) with thin and/or generic content and have most of their inbound links focused around a relatively small set of URLs or that are not generating regular inbound links have seen the biggest impact.
This shouldn?t surprise anybody in SEO land as unique content, good site architecture and strong backlinking have been the cornerstones of SEO for years. That said, it appears that this algo change has raised the game to a whole new level. It used to be that an authoritative domain could add pretty much any content, even duplicated content, it wanted to its site and with a little bit of effort get strong organic traffic. That does not appear to be such an open and shut case anymore.
Neat about the authority domain stuff, that's what I said earlier.

Some of what he is saying about the link focus and smaller set of urls that are not regularly visited also falls in line with some of the other contributions here.
He goes on to make a list of suggestions to combat these effects, they are:
- Get unique content on your business profile pages and other important pages (and I?m not talking about just putting Yelp and Twitter feeds on them). You need your own user generated reviews, editorial, q&a forums, etc.
- Consolidate the number of pages you show Google and limit them to only those that are ?valuable? (i.e. have unique content and/or inbound links). This one?s tricky as it?s hard to know on a large scale which ones are the best.
- Continue or start to drive links to deep URLs
- Make sure all URLs are as close to inbound links as possible
- Prioritize valuable content in the architecture so that they are as close to the home page and other valuable URLs as possible
- Do something remarkable with your service that gets people talking about you and linking to you.
A fairly standard list, aside from the user generated part. I would imagine not everybody does that. 3 out of 6 are all about site structure, and the other 2 are about links, specifically do something to gain links naturally, and get links to all your pages no matter how deep they are (if you aren't doing that, well DUH!).
This raises another factor that none of us have mentioned, which is user contributed content. I think it's possible that this could indeed contribute significantly as a quality signal. Not so much in terms of the content itself, buy by having access to contribute all such content. From a user perspective, getting first person input/response certainly could be considered a quality experience. As long as the response you are getting isn't 'shutup you stupid asshole'.
So what does that mean? Throw up a forum, a pligg, and of course the blog to allow for more user interaction options? This would explain why amazon recaptured their traffic, because every one of their product pages now allows for forum interaction and discussion of the product.
He said nothing about CTR or bounce etc. Perhaps rightly so, as they are factors that are not very reliable in measuring I think.
Think we are getting closer.

Thoughts?