Maybe this is of interest, but the first social network I remember using was actually a "dating" site, when we were in our early teens, around y2k, there were no other kinds of websites (that we knew of) that were general-purpose enough.. So everyone I knew rushed onto some site called weblove, and we used it as a general hangout, it had forums, chats, "mail" and the ability to build a profile and upload pictures.
Sure, boys and girls talked, but dating was not a focus. It was actually a very nice social platform, encouraging meeting and communicating with other people in exactly the way facebook does not. Also, it was free to use.
A dating site doesn't want users to be able to associate with each other without both ends paying the matchmaker.<p>A social networking site wants users to connect and intermingle as much as possible so that they can extract metadata and assocations for monetisation.