aristotle - 12:44 am on Aug 24, 2012 (gmt 0)

user-data signals that sound like browser data to me (did the visitor scroll, hover on a link, bookmark, etc?

It hard for me to imagine that Google wouldn't use such a gold mine of statistical information about users' interest in a web page. If Google really wants to improve the quality of their search results over the long run, then surely this is the way to go.