This is wrong thinking. Nobody can really control when someone takes a nefarious interest in them. Public identity is only fine if there's nobody out there who wants to harm you. But since you can't control who wants to harm you, you can't really decide in advance if having a public identity is OK or not. The answer isn't "stay off the Internet" which is tantamount to "don't leave your house." This is why Facebook tries to put controls in the hands of the tagged; they only did that after a string of teenage suicides related to cyber bullying. Surely these kids thought they had no reason to be so concerned. But it turned out they did, they couldn't control the damage done to their reputation, and killed themselves.

Your coworkers aren't the only people in the world who might have interest in what you have to say.