Looks like Amazon thinks it is useful as well - the rumor is that they have invested $1M into it (just think if they added added the ability to create your own bookshelf from amazon.com).

http://www.techcrunch.com/2007/02/25/amazon-invests-in-shelfari/

Sincerely,
Ben

Ben Watson, ben.watson@thomson.com
VP of Collaboration - Thomson NETg