Website trust/credibility factors. I believe that Google asked users to evaluate a sample of websites during Panda's development. This sounds similar to what Microsoft did in their recent website credibility study [webmasterworld.com...]
I am pondering anything that can be programmed into the algorithm to be an indicator of quality, in particular, "Reputed Credibility" (i.e., 3rd-party certifications and awards). Among these MIGHT be SSL Certification, privacy verification, hacker-free certifications, respected/recognized awards, etc. These may or may not be playing a role right now.
On a different note, I wonder if external links that are blocked by robots.txt at the destination or somewhere en route during multiple redirects (i.e., affiliate links that are blocked at the destination or at an intermediate redirect -- similar to what happens with CJ links before they are redirected to the final destination) could be a quality indicator.
Another item I am pondering: author names. I wonder if profiles could be created for author names, similar to any other expected query/phrase. If an author tends to be published on hubs before/after they have contributed works to your site, maybe this is a negative (particularly if those hubs have been hit by Panda)? I don't see many author names or "staff writers" listed on articles of top ranking sites in my niche. This could just be my over thinking, but I have seen my contributors publish (unduplicated) works on hubs (a reasonable expectation if they are freelance), so I fear their name on my site, in and of itself, may be bad.