I've noticed a bit of a trend. Like, this morning Rangerwickett was talking about his GM, and it was someone I'd never heard of. So, it seems like there are a lot of people on here who are fairly well known, and the others in their group - if they post on here at all, are exceedingly obscure folks with less than a dozen posts.
At first I thought you were trying to see who on here gamed with who else, but you're asking for something a bit more obtuse for that. That would be interesting...
I currently game with 'drife', he has, I think 10 posts to his name. I don't know who else he has gamed with. We've also added a couple of new guys to the group, and that latest one might have an account on here, I haven't actually met him yet.
I used to live in Kansas City, and gamed with a bunch of folks who didn't post on here. One ended up making a user id 'rath lorien' to post comments in my story hour. I think he has maybe 3 posts. I moved away, and my friend reddist (who probably has a couple of hundred posts) now GMs that group. I don't think anyone else in that group posts on ENWorld.
ENWorld game days are going to muddy this up quite a bit. I've gamed with Henry, Gerzel, Urbannen, Cthulhu's Librarian, GMVictory, Ruined One, Shemeska, Clueless, and a bunch of other people I can't really recall off the top of my head. I'll be adding more to that list after the MD/VA/DC game day coming up.