There's definitely been a shift; partly it's because it takes a lot of time to post to groups; I'd post a fic in about 5 places; hugely time-consuming. Also the places just shut down after Buffy/Angel ended. And finally, when everyone was on LJ, and eventually it seemed everyone was once the invite codes weren't needed, why move off it?

I used to subscribe to a dozen yahoo groups; might still do, but apart from one, not fandom related, they're all on 'don't read; and I haven't visited them in months.

And, no, not your imagination; I remember that, too.