I see in the update that Google have added something similar to librarything to Google books but without the social aspect, the emphasis is on research not socialising although the tags and personal libraries are accessible to others.
Just an interesting aside, Kingston library have incorporated" library thing" into their public catalogue good on them, worth watching to see how the community use it.
I decided to check out one of my favourites web 2.0 tools Zotero (really useful research tool only available with Firefox browser) and yes, updates were available it now can search, upload ,link export and take snapshots of flickr ,you tube pages as well as many other formats and provide a wider range of citations. You can snap shot a web page see it within the tool highlight sections and add side notes just as you would to hard copy.