just a couple of other thoughts to add to what marty wrote: consider: if you log in daily and read a thread that is active for (say) a week (surely that is conservative), you will personally be adding 7 views to that thread -- now how does the ratio look, and how many voyeurs could there be? [my math tells me that the participation, even covert, is more geometric then additive.]
also, I made reference elsewhere to the "Word Fugitives" forum at the Atlantic Monthly website. there are many similarities between this board and the forum that Barbara Wallraff administered at Atlantic Unbound 1 to 2 years ago -- it never got quite as silly there (not saying that this is necessarily a bad thing), but there was a core of regulars who probably tended to dominate and the thing ultimately died from the lack of a fresh infusion of contributors. you can see the remnants of this in the Word Police and Word Court forum.
