But none of these services do anything that wasn't already available via incumbent technologies (which were somewhat inaccessible to non-geeks), e.g. BBSes, Usenet, IRC, IM, web forums, etc., and people have been developing more accessible iterations of these types of technologies (reddit, for example), and people will eventually migrate away from the constrained, privacy-compromising services like Facebook into the wider internet.
People say that the open web is dead, but I think the walled garden approach is never really long-term sustainable.