I had known I was ABDL (or rather, knew I liked diapers) before the Net but I remember a.s.f.d. very well.
I'd first heard of it from a free computer magazine whose name I forget; it was widely distributed in the mid 90's and most people on the net in that era had read it.
The article was yet another primer on Usenet and the alt.* group hierarchy. Alt.* is Sex to most and the author was going on at some length about the weird fetish groups. He said, and I remember this very very clearly for 15 years ago: "...groups like alt.sex.fetish.diapers! Please don't ask!"
At the time, I thought, "Why yes I will!", and opened up Forte Free Agent and burned more dial-up time.
I almost never posted on that group; I was very paranoid and still am to an extent (I have two blogs, a website and a presence which, while not Robert Scoble's, would not be helped by my admitting to my fetish publicly.)
I posted a few times via the anon@penet.fi address; if you remember that first hand, you are a real Net old-timer. When that was shut down, I never posted again. And as this was around the time people needed to use tildes to indicate authentic content, that was it for a.s.f.d and me.
What I really miss from those days were and are the stories. A.s.f.d saw much of its fiction posted during a time before Usenet was archived to any extent. Deja News, the early news archiver, didn't have any a.s.f.d content and had they not been bought by Google, they may have trashed their database, or so the rumors had it at the time.
I had a selection of stories from the group on a Zip disk, which got corrupted so I had even fewer. Many stories from that era do still exist on the net, but they're widely scattered. It was only recently, for example, that Kevin's story series "Ashley's Diaper Adventures", a mainstay of a.s.f.d, returned to the Net. There are many favorite stories that I can only remember, disappearing from the net.
Lil'Jennies Infantilism site, still around, is just about the only reminder of what a.s.f.d. was.