These things tend to move in waves. Somebody comes up with a great new communications platform, and everyone abandons their custom solutions for it. Then the technology behind that platform becomes commoditized, the knowledge becomes widespread, and people start coming up with small scale custom solutions again. Then one of those custom solutions decides it wants to be big, generalizes it's platform, people flock to it, and the cycle starts over again.

Give it a couple years. I bet we'll see people creating their own social networks again, in some nearly unrecognizable form.