Apropos of nothing, del.icio.us has zero egoboo. There's just about no way to distinguish one user from another other than by their bookmarking behavior. With the outbound link on the profile page, you can do a bit of namebranding, but that has little import for how good a user's link stream will be given the varied ways people use the system.
I wonder what an appropriate network growth model for del.icio.us subscriptions would be and whether the system actually conforms to it.