It's hard to claim to be introverted when you have a blog that's <yourname>.com and tweet private thoughts to 700+ strangers several times a day.
I mean, I'm thrilled that a random article that I stumble on from the iPhone PPK post is getting a surge of readers. Feel like I connected people in a small way.
I know a few introverts who constantly connect with about a hundred contacts through Twitter (I was relieved when Twitter added the @filter)
Technology levels the playing field for making & building human connections (whether it is one-to-one, one-to-many, uni/bi-directional). Introverts can leverage technology to build and nurture communities. And, yes, make a living doing it.
And, I'm going to assume the extremely influential Daring Fireball's Jon Gruber is an introvert based on what I've read about him and his articles and the fact I've never really heard of him making public appearances.
For Meyers-Briggs I've tested as an INTJ (taken at a previous job), and ISTJ in a personal test. Since I scored the personal one myself, I could see my scores in S/N and J/P were very close. In examining descriptions of the types I'd tend to classify myself more INTP/INTJ - clearly recognizing the traits of each in myself, but the only section I'm truly certain of is the I and the T.
I also tend to disagree that a person is one way online versus offline. I know I suffer from anxiety, but I have no problem standing in front of a crowd making a presentation for which I'm prepared and/or confident in my subject knowledge. That does not indicate I don't suffer from general anxiety though. I'd say it's the same with introversion. I could have a blog or tweet, but I think you'd notice a distinct difference in tone versus an introvert and extrovert, or how much personal information is shared versus professional. I'm sure there are introverted bloggers just as there are introverted journalists, actors, musicians, and other professions with a high public profile. The 'public' nature of what one does is not what defines their personality traits.