Glad you said that!
I thought the HBD would perk up, but it did not.
Yeah, I think the people who were/are interested in those formats aren't interested enough to actually post!
When you make a big change like that, you pick up new people, but at some point you drive others away. I would guess that a good number of people on Tech Talk moved over to the forum and found they liked it (or at least, didn't hate it), while another group said "the hell with this" and went elsewhere. It's easy to throw around the Luddite label or talk of the march of progress, but sometimes one person's shiny new thing is another person's annoyance.
Perhaps sometime in the not-so-distant-future there will be cries of how we need to retire the AHA Forum and move everything to Facebook because everybody uses Facebook now, it has all these new features the Forum doesn't, and that other brewing forum moved to Facebook and we have to too if we want to keep up, etc
. When that happens, maybe you pick up new people, and you'll probably lose other people for good. (Then the Next Big Thing after Facebook comes along (it will undoubtedly have to do with Big Data and clouds and new paradigms and stuff) and then we all have to move with it....)