A definition of social information retrieval?

It's pretty evident that information retrieval in the web rely, among other things, in mechanism based in a bottom-top logic. Pagerank harness individual decisions to give relevant results in the queries, and this has a social and "democratic" logic and, up to now, it's the best way to retrieve information from the never-ending WWW.
We can think of this outside the bounds of the Internet. We do search for information in brick and mortar life looking at what other people do or tell us they do (word of mouth). We can do a lot of this in the Internet, a perfect place to nose around, and even better since we have applications like del.icio.us or myspace that invite to do social navigation. Furthermore, other applications have mechanism to retrieve our opinions (digg, or any other place where we are asked to rate) o simply do the job for us, as Amazon or Pandora collaboratively filtering.
Retrieving (selected) information is very related to what a users want to do in a thematic portal, so, as this is the context of my phD, I bookmarked on the spot the SIRTEL07 workshop when I first saw it. Despite the interest of the papers I found there, no one of them gave me a clear definition. So I googled around and got this:

Social information retrieval systems are distinguished from other types of ir (Information retrieval) systems by the incorporation of information about social networks and relationships into the information retrieval process.

The paper in interesting but still is too much centered on searchers and not on social navigation and all the other stuff I mentioned before. Eventually I found better, but still in press: a book on social information retrieval that is considering it very widely, from algorithms to social bookmaking and even design.