Michael Geist has written a good article on the BBC news site about the ‘walled gardens’ of social network sites such as MySpace which at the moment means that to have a complete social network you’ve probably got identities on several of these sites which need maintaining, rather than one which can be linked or shared with the other services.  The full article is here : BBC NEWS – Technology – Pull down the walled gardens.

In addition to Michael’s point about interoperability is the information about which sites are most populate in different parts of the world.  For example Facebook is the leading site in the UK, but Bebo is in Ireland and New Zealand.