Whoever you are. 
Thanks to my occupation and a few threads which have gained some fame (notoriety), I think I’m recognized by most dopers.
Most of the names here are familiar, but I can’t necessarily associate a posting history, set of opinions, or other personal details with those names.
I’m pretty sure when you announce you’re a conservative, the Dopers put up a “watch out for this guy” picture, like they do in the post office.* So I’m pretty sure I could hit the 20s or 30s easily.
*Do they actually do that? When I remember to look, I can never find any photos.
I think I’m recognizable to a few people in two weirdly different demographics - slightly crunchy parenting people, and Left 4 Dead (2) players. 
There are several names I’m very familiar with here, and others who have been on the Board for a long time and/or have many posts that I don’t recognize.
Which and how many forums I regularly frequent will influence the posters I’m familiar with and who are familiar with my name. For example, I’ve never looked in The Game Room; I usually frequent MPSIMS, IMHO and The Cafe Society, so I’m more likely to know and be known by the denizens of those communities. What that number is, I really have no idea. I’ve interacted - that is, responded to or been responded to - many posters over the years. Whether they can remember me, I obviously don’t know. It might have been easier if you had asked how many posters we know.
I recognized all the names except for a few who’ve been around for less than a year. Covered in Bees I remembered, even though he (she?) is kinda new.
I chose 20+. I post mostly in Cafe Society, in the Whatcha Reading threads, and in the Mad Men, Wire, Dexter, and Deadwood threads, and I’ve been around for awhile, so 20+ seemed reasonable.
I said 20+, but I really haven’t a clue. I’ll assume that since I’ve been around for years, a reasonable number would recognize my handle and the mark of quality that it represents :D. On the other hand, I don’t seem to ever get name-checked in the threads where people discuss user names.
I picked just a few, if I’m lucky.
No-one really likes me…:
::
Now you - you are memorable. In the best possible way.
So, uh, who did you used to be? I used to be featherlou, in case anyone is wondering.
That’s one of the reasons I went low on my guess - I’ve been around a long time, and have lots of posts, but I’ve never been controversial plus I changed my name this year, so I think I’ve thrown a lot of people off my trail.
One of these days people will get my gender correct.
There have been threads where I more explicitly state that I am a guy, but a quick Google search didn’t turn them up.
I’m…guessing I’m somewhere around “tolerated eccentric,” kinda like a joke supporting character on a sitcom.
jali, I recognize you all the time. Ever since you posted your picture that time, I always put a face to your name.
As for me, I’m not sure. My posting frequency has been erratic lately and my screen name is easily confused with others. Also, people get me confused with my twin sister…even though no one here has ever seen us in real life and we only occassionally post in the same threads! I still find that amazing.
So I’d say I’m known, but not enough to get a superlative in the Straightdope yearbook ;).
Ha! I remember at least one thread where you cleared it up, but I didn’t remember the result. I’ll probably forget again in a few minutes.
I said 3-10, mostly because of the MMP.
I think I underestimated because I hadn’t taken into account the Dopefests I’ve been to. But if I were basing it purely on the number of people who recognize me with any distinction from various threads, 3-10 probably fits.
Mafiosa
I didn’t think I was that memorable, but from a comment in another thread it seems I am. So… I’m going with the 20+ option, but I have no clue. I should probably get some help on this. Dopers, if you recognize me please send a warm gushy note on how awesome I am to the M,I,S! Fan Club. Getting my gender right gets you plantinum membership.
So what does overlooking your typo get us, girl?
Your name is too damn weird too forget, so I’d put you at the 50+ level myself.