I know most of you are internet savvy and don't need to be told that, yes, a future employer or whomever might look through your web pages to find out who you really are, but it does serve as a reminder.
I do know that people at CMU googled my name when they were looking through the resumes, since, well, they mentioned finding my arrest picture! Fortunately in that case, it served as a conversation piece and probably points in my favor. But as a note, this is one of the very few reasons I might lock down a post.. not that I care if most people will see it, but it's not something I want a casual browser trying to figure out who I am to find.
Anyway, I wanted to segue into another point not made by this article. Do read the terms and conditions of any service you use. Many of these online storehouses of information ("Post your pictures or mp3s here!") will insist that anything you upload to their space suddenly becomes their property. This is dangerous, and should be checked into before you decide to use a service, regardless of whether it's the latest thing.
Fortunately, Livejournal considers all content a member posts to be the sole ownership and responsibility of that member, though they might kick you off the system if the content isn't legal. I've heard that MySpace.com's policies are different, though I really don't feel like wandering about TheirSpace long enough to verify this.
And I end my public service announcement (WITH GUITAR!).