Well we already know that most people here already either respect me or hate my guts, so I don't see it making a difference. But mostly, I just don't want my clients googling my name and finding this place among the search results.
And to some extent I don't want the previously mentioned "hate my guts" crowd to have an easier time finding me and keying my car.
I totally agree, of course I'm not that dumb and whenever I need to send a email to either Aaron fisher or some friend, I sign it with my real name.(for reasons explained above)
But that's actually it, we have avatars on internet for security reasons, and as steerpike pointed, I wouldn't like people to google my name so that they could find 700+ results on my geek forum daily chores.
I am against the thought of having your "real name on a internet forum" as a rule of thumb to be "professional", If I ever make a site about me or whatever then I will use my real name, but for a internet forum full of strangers? You can call me RD. Or Chopper. Or RDChooper (yes people have writen it that way).
By the way, Zack has a cool sounding name for a magician.