crobb305 - 3:50 pm on Apr 13, 2011 (gmt 0) [edited by: crobb305 at 4:29 pm (utc) on Apr 13, 2011]
I think you're on the right track. Ten years ago, links were all Google had to determine PageRank. Then they developed TrustRank using additional authority/quality signals. Now, surely they beginning to using share data. If there was ever an opportunity to rank content based on votes from "the little guy" who doesn't have a website from which to "link", this is it. With the world of emailing, sharing, tweeting, liking, and even printing, there are lots of signals Google could use as a vote of confidence.
Heck, my 60-year-old mother has a FB page and shares content with her friends, but she never had a "website" and never understood the concept of "linking". So now, with FB, she has a voice on the internet and her vote can count. Having said that, similar signals have existed for years (bookmarking, for example -- I have had a "Google Bookmark" button on my site for 3 years and I am unsure if it has even made a difference). Side note: I tried to get my mom to sign up for the +1 experiment, sent her the instructions, and she couldn't figure it out lol. I haven't looked at it, so I assume it wasn't working, or it was too complicated or not readily apparent to her -- not a good sign if she can use FB, but +1 was too confusing.
At this point in time, I'm not certain this update has incorporated any sharing data (or fails to do it effectively). I work with a site that soared during Panda that doesn't have a FB page, no share buttons, etc; and another site that tanked, which has a FB page with 1,500 fans. Granted, these are just two examples, but I have seen more.
I still feel like there are more on-page factors being used with this update: ads, little/no content, poor (or excessive) internal linkage, and possibly some external signals like certifications that can help with branding (I see a lot of newly ranking sites with SSL and other trusted certifications).
[edited by: crobb305 at 4:29 pm (utc) on Apr 13, 2011]