Well, I do post on google plus using my real name, and I don't know why that should be a problem. I just use something else if I want to remain more or less anonymous.
Google plus is a tool that I use to share information with friends, family and acquaintances who already know my name. I'm relatively careful about the things I post on the Internet, and don't think I would or should be ashamed about anything I ever said online.
I've never seen any compromising pictures pop up on the net (at least not with me on them).
I agree that google knows a lot about me, but as long as they don't share any of this information with third parties and just use it to give me better targeted ads, I'm al for it. Ads are what makes large part of the Internet possible without having to pay for almost everything, so better ads make them more money and are less of a nuisance for me (yes I sometimes see an ad that's interesting yes I tend to click on it if that's the case)