An asymptomatic carrier is one who exhibits no symptoms of the illness but is carrier who can infect others. I don't believe that is the right analogy here.

With herd immunity you have a group with a large rate of participation, which effectively immunizes those that haven't been.

Facebook is the opposite in that you may not be "infected" but if everyone around you is "infected" you might as well be, because Facebook will piece together your information based on what your friends make available.

Plague almost starts to sound like a better analogy...