The second point he makes has something in store for research librarians:
2. Flickr is more editorially controlled than Fotolog. The folks who run Flickr subtly and indirectly discourage poor quality photo contributions. Yes, upload your photos, but make them good. And the community reinforces that constraint to the point where it might seem restricting to some. Fotolog doesn't celebrate excellence like that...it's more about the social aspect than the photos.In other words, not all communities are equal. As academic libraries, we cannot and should not aim to build communities of maximum size. This is where our long tradition of quality over quantity comes in. If that means, for example citeulike won't be as popular as del.icio.us, so be it. They can both exist.
(on a sidenote, flickr has some serious i18n work to do if their marketshare is so low outside the comfortable-with-english world)
Related to this: social networks need traction from an active community to flourish. They need numbers. That's why I think the use of del.icio.us for the Avian Influenza Resources-page from Umich's health library is perfect. For everyone: the library, they didn't need to build something themselves; the users of the library, who gained a good resource; and the wider community of del.icio.us users interested in the topic, since the work the librarians did helps improve the general body of information in the whole system. I have much respect for my colleagus who built the brand new HvA web resources site, but it's no match.
As libraries, we cannot compete. We shouldn't. On the contrary, we should embrace cooperation, as we should embrace change.