I visit another message board concerning NPR's Sunday puzzle, and it sees weekly posts and replies based on solving the puzzle. I think the forums lack the same incentive to revisit as regularly. There was always the appeal of socializing with the forum regulars, but I think many regulars have simply aged out of perusing forums (being an adult takes up so much of my time!) And without a steady influx of newer members, it makes sense that posts nowadays are few and far between.
Guess I'll have to search for people on Facebook. :p