An interesting thread and observation. My reasons for not having posted much at all in a long time are several, I think. I had a roasting from one or two on another forum a few years back which left me thinking they weren't interested in a mature debate but rather a character assassination. I was probably very thin-skinned, but since I posted on fora for fun, and that didn't qualify as such, I just lost interest in posting very much. Since then, the economy has stopped my flying completely so I've lost touch with what's going on in the field. I'm guessing that's a very large driver in the overall decline in activity.
And, finally, I guess I haven't felt like I've had too much to say on too many topics. And, I have to admit, I've moved my daily reading to JB which seems much more entertaining. I don't post there, either, but I do read it every day.