When I was in college, my roommate and I got into a discussion about brushing our teeth before we walked across campus for class, whether we even needed to.
In our stupid male brains, we thought there was some chance, no matter how remote, that someone might want to makeout with us on the way... I mean, it was highly unlikely, but what if that hot girl in our English class caught up to one of us and just couldn't resist herself from planting one? Hey, you never know.
But if it ever did happen, wouldn't you want to have the freshest breath possible? How awful would it be if she pulled back because she tasted garlic from your lunchtime chicken roll. The small incremental cost of brushing our teeth far outweighed the huge, but infintessimally unlikely, downside of that awkward moment.
That's what I think about when I manage my digital self. You might think it's sort of unlikely that anyone might want to hire you from your blog, Facebook profile, etc... but I just encountered a situation the other day where a friend's personal blog actually went a long way to helping her connect with her potential employer, b/c of shared music tastes and just her overall familiarity with technology.
So, if you have an outdated blog, don't manage your LinkedIn bio, or have some "not ready for primetime" stuff on a social network, take a moment to update it. Hey, you never know.