My face to face group is three people and I am the only one on Enworld. Im my email games, I have about 20 players in various games and as far as I knowo nly about 2-3 of them are on Enworld.
My immediate group that I usually play with is a half-dozen. Of people I know in the area who game, we are again approaching a dozen to a score who don't use En World, (or Wizards.com, or, really, any online resource).
The groups I play with consist of about a dozen, and besides me I know one that fairly regularly visits (and I suppose he has an account, I haven't seen him post anything), and a couple more that may have accounts (and at least have visited from time to time).
So, somewhere in the vicinity of 16-33% of our group have used EN World.
As far as I know, I'm the only one in my group that visits EN World. I don't know if any of them are really forum users to be honest. 4 of them play MMORPG so I imagine that's where they spend most of their "online" time. That's fine with me. It means I can discuss my game and get help with devious plots here on EN World without them seeing!
Of everyone in my current group, and from older groups, as far as I know I'm the only one. I've tried to get some friends from older groups to come check ENWorld out, but they only seem interested in playing WoW.
I've met maybe four people in my entire gaming career who visit any rpg forums at all--there might be others but none of them commented whenever the forums were mentioned, which leads me to believe that most gamers don't care or don't know of the forums.
I know probably 20-30 other gamers, at least casually. Some of them go online, but I don't know any of them who come here. I play with one DM in an online game who comes here occasionally.
Of the players I know well (5-7) I'm certain none of them visit EnWorld. I've heard of one other person in my community who is on EnWorld, but I've never actually met him...