I'm guessing you know my first name along most every person here on Hacker News? Color me skeptical. I consider my interactions here semi-personal. The interactions I have in other places are quite personal. There is a gift of anonymity, and that gift is the allowance to be a only a small part of your real person for a few fleeting moments.
There are many honest reasons I don't want my real name associated with everything I do. Sure, I have my real name posted in various places, but that is because it is my personal and strategic choice, not a point of coercion from a company. Choice is very important to me.
Just imagine this: suppose you wanted to blog about something that could possibly be embarrassing or things that you aren't even talking to your wife, parents, or best friends about. I'm not talking about murder or anything, but things about yourself that are deeply personal and you have nowhere to turn to vent or get advice. The fact is that you are not willing to be vulnerable to people in your real life, but you'd like an outlet and opinions from others about your situation. Believe me, I've posted things in forums and other places about myself that are deeply embarrassing and disturbing. I don't want my next girlfriend to know and I certainly don't want my next employer to know about this stuff.
There is a certain class of people that don't want their entire lives spread across the internet. Heck, I'd venture to guess that your email is not jason@_____.com, and if by some early-adapting miracle it is, most people you interact with is not.
Suppose you wanted to create a G+ account to talk about your frustrations with anything. Would you be willing to be honest and forthcoming if you had to use your real name? Would it be at all entertaining or useful to other people going through the same things you are?