I know at least a few of my readers are fellow alt.fan.pratchett veterans, and so will know all about the social dynamics of internet communities. About flame warriors and trolls and vampire threads, about inside jokes, meet-ups, and very real friendships and even marriages that are born in text only.
Some of them have also done IRC, and also know about flooding, and being kick/banned by the channel op, which is the natural result, about moderated and unmoderated channels, about /msg and /dcc, about lurking and joining topicking.
Some may have done fidonet, dial-up BBS, AIM, mailing lists... I've done all of that except the dial-up BBS, but I've got The Discovery Channel Bulliten Boards (alas, now vanished, as far as I can tell) and the Prodigy message boards too. And personal webpages. And public profiles. And now I've got a blog, besides posting comments to other people's.
So for those, like me, who remember when some of the slang in the jargon file was invented, who sometimes think in acronyms... I present a link which, unlike most of the others here, you may actually not yet have seen. Via Teresa Nielsen-Hayden an interesting essay on designing social software.
And, as an aside for people who want to use social software to communicate top secret information, a link I just found while browsing the Jargon File: a biography of Alice and Bob. Remember them?