I was wondering that myself. There are a lot of members who signed up a long time ago and have not posted. Maybe just people who signed up on a whim and never came back...maybe just lurkers...maybe just here for the free photo hosting.
This in no way takes away from the great job of all the admins and mods here...fan-freakin-tastic.
If there is anything the nonconformist hates worse than a conformist, it's another nonconformist who doesn't conform to the prevailing standard of nonconformity.