He admits he's in denial about social networks. Still, he scores some key points when he says:
[...]I believe that best functioning communities are those on mailing lists. No shitty scrapbooks, no request for contacts or recommendations, no virtual request for pass-the-baton stuff. And they get work done too. I’d like to know how many active communities—who really get work done—are on Facebook, or Orkut, or on any other social network?
As far as I know, everyone of those GTD communities are on their own mail lists. They dish out solutions before you can compose your next email. Have you seen it happening in these so called web 2.0 social networks? [...]