Maybe this feature has been there since the dawn of time, but today I noticed that when doing a Google search, pages that I have bookmarked (in personal search) now lists the category of the bookmark (if listed) and any comments I've added.
Example:
http://picasaweb.google.com/topdawgnate/Web/photo#4956156877924663314

Everyone on the Web2.0 kick has been sputtering about social networking (and to they're credit, you can't deny myspace). What if in combination to with the Google Co-op account you could subscribe to other people's bookmarks and comments? A qusi social networking incorporated into search results (maybe even a rating system involved).

this is an interesting theory..what happens if an API is launched for this concept ?

I am pretty sure that is new. I have even stopped commenting on my bookmarks to stop those comments cluttering the results.