Social Bookmarking Explosion

Social bookmarking has entered its heroic age, where multiple actors content for a new, growing world.
In the begining was del.icio.us. Elegant and fast, crisp and focused, Joshua's invention was rapidly taken up. In tandem with Flickr it kicked off the folksonomy furor. Furl was there as well, if relatively unsung.

Others have started to emerge. del.irio.us took things a little further. I have recently found RawSugar, which positions itself to attact del.icio.us users, and adds a bit more personalization to one's self-presentation. The same day I played with Sugar I also spotted Shadows, which wants to heighten bookmarking into larger commentary on web pages (NB: site seems to be down tonight).
B tells me about Connotea, which is aimed at the sciences.
The Wikipedia's social bookmarking entry lists still others. More than thirty (30) others. Are we seeing social bookmarking entering the YASN (yet another social network) phase of that movement? Is the duplication of effort going to grow? How much innovation can be attached to each new one to justify exporting one's growing list of links?