tcv, let me explain myself more clearly
Shelfari wants to follow the on the success of other web2.0 websites but in my opinion they missed the point.
The idea of web2.0 is that they provide you with a free service that is attractive to you; then you along with lots of others will start using their site. By aggregating lots of people they can offer other kinds of services that are basically data mining.
Look at successfull web2.0 services:
del.icio.us: manages your list of bookmarks (better than your browser)
then they have a lot of bookmarks from a lot of poeple, so they can start suggesting you sites in a topic
Flickr lets you share your digital photos with friends and family
By making your pictures public they can be shown to other users, you can also see their pics etc. etc.
In the case of Shelfari they want to build on aggregating lots of users to find related content, but I don't see what is the attractive free service they are offering. Compare my motivation to use their site versus using del.icio.us or flickr...
So in my opinion they will not have a large user base and they will vanish.
