That's more or less what I was going to say, too. Speaking as if it were me facing the choice, I know I've gotten weirded out enough when I get anonymous comments from people who presumably stumbled across my LJ from the link I used to have on my Facebook page - I wouldn't want to have to obsessively worry about how many of my fans were digging through all the random junk I posted way back when and forgot about. If it were me, I'd either friends-lock most things here and leave a few select posts available to the public, or create a new journal for interacting with the public and not give out this one.

Of course, given that you're writing a book *about* blogging, I can see how there might be a few more complexities to it than that, and you're already far more used to dealing with a huge readership than I am. All I can really say is, go with your gut - if you want a name change, do it; if not, don't.