Have you ever posted your name to an online bulletin board, proclaiming that so-and-so was a you-know-what, only to change your mind after learning more facts? Did you wish it would just "go away," only to turn up again when you least wanted it to? I'm here to tell you that if you post something online, it's there FOREVER!
Quick example: Do a Google search on my name, Phil Gerbyshak. OK, just click this link. Over 90,000 hits with my name attached. Hopefully they are all complimentary references, or at least ones I created online. But imagine if they were ones that I had made blasting a former employer, or ex-girlfriend. What would that story tell you? Even if I tried to remove the links, they might NEVER be gone. If you notice on Google, the link to the right of the URL is a word that says "cached." Cached means Google took a picture of what the website USED to look like, and clicking the cached link shows you that picture Google took. Other search engines may eventually do the same thing.
Now change the searched name to your name, and see what turns up. Anything you're embarrassed about? How about that MySpace profile that links to all your friends' pictures at frat parties? Is that really the personna you want to share with the world, and especially with potential employers?
Now don't think for one minute that potential employers aren't doing this very same thing when you apply for a job. If you've got nasty stuff out there, you better make time to put something more positive out there, that you control. Write some articles, put up a website with your resume on it, whatever, but get SOMETHING up there that doesn't have you playing quarters with your friends. If you don't, the only impression you'll make is a bad one. After all, diamonds are forever, and, for better or for worse, so is what you write online.