Another timely and insightful Cringely reality check; see the full post for more context-setting
Marshall McLuhan argued that obsolete communication technologies survive as art forms. This is true, I'd say, for Morse code and movable type printing and perhaps even for your venerable Rolodex or typewriter. But it isn't yet true for CB radio, nor for most Internet technologies. Maybe they aren't old enough yet to be appreciated. In the case of CB I think range of reception limits the possible population of players to something less than an artistic critical mass.
What will likely happen to social networking is that some applications will survive on a more modest basis than now (used by the trucker equivalents), others will morph into some new Next Big Thing as their more compelling sub-applications take over, and true hard-core social networkers will jump to more advanced technologies that eliminate the riff-raff. In the meantime, 70 percent or so of most social networking functionality -- the really useful functionality -- will be sucked into the dominant portal/search/e-mail/chat/social networks like MSN and Yahoo.