I once asked for a post of mine to be deleted from a (weird pagan) discussion board because I accidentally posted it with my real name on it. Didn't particularly want people at work to google and then start making probably wholly accurate assumptions about me. It's still up there now, and even if posts are deleted (or whole blogs commit hari kari) it's all still out there filed away somewhere. Try clicking on cached when you google something and the page has been taken down.
I am continually wrestling with this privacy/identity border, I don't put my real name on my blogs (except occasionally in the third person, which is silly) because I know that it could affect me at work. But its virtually impossible to prevent leakage as soon as you start stepping out of the blogosphere into the fleshworld. For instance as one of my blogs is South East London-focused I got invited along to a Lewisham Bloggers drink, got to know people some of whom I found I had real world connections with (kids, neighbours etc) so now quite a lot of people know my real name and occasionally mention it on Facebook etc.