I had noticed a down turn in this site and another plant specific site I visit occasionally in the time after the subprime housing lending bubble popped. I just assumed that there were fewer people with expendable income to play with and that led to the reduction of activity on here. There is also the proliferation of time wasting sites (I won't name names, but you know them).
I've seen worse as far as not having active mods. The 6 months to a year before the current owner took over were tough on the couple of active mods we had then.
I am barely in the hobby anymore, and have trouble being interested in participating here because of that. I'd like to do more with it, but it is what it is for now.