I think these things probably go in cycles.
We had the movie cycles of interest that really brought a lot of new members, then a small-scale cycle over CofH. I guess the next ones will be for The Hobbit.
The cycle of the year, in the UK at least its lovely weather (shock-horror!) so less likely to be at the computer. Also there are the usual ups and Downs
of the working/student year, holidays etc that all influence activity.
Like Formy, I have a quick check most days to see what's new, but post more rarely (was never a volume-poster though!). I guess we each have our own personal cycles of interest and activity too.
Maybe one thing to consider is that t'internet is a bigger place now, and more into Facebook, Twitter etc applications than bulletin boards maybe.