Comment Re:Facebook Soaks Up More Free Publicity! (Score 1) 314
Its value as an SSO is, I would think, unrelated to the number of personal connections on there. Metcalfe's Law does imply, however, that the social value (and likely monetary value) of Facebook is enormous.
An SSO really shouldn't be concerned with how many people are actively using it. It should be concerned with being a valid means of authentication for as many sites as possible such that it is a truly viable SSO.