I'm on two nowadays (this, obviously, being one). I've been on lots in the past. I suspect that message boards like this are rarer than they used to be, because people now use Facebook, Twitter or both (and others) instead. I'm in loads of Facebook groups: I recently pruned my list, by leaving many that I never posted in. Then there's Yahoo groups, which are whole different kettle of fish again. It's hard to remember, sometimes, what life was like pre-internet (which for me means pre-2004).