Depending on how much of your personal information you share on the Internet, such as postings on Facebook, Twitter, or any of the billion other social networking sites that are out there. You might have left a "online presence" (e.g. comments, pictures, etc.) that might not best represent who you really are.
If you're current or future employer, significant other to does a quick check of Google, Bing, Facebook, Twitter, etc. What will they find?
There are somethings (such as, public record, postings, etc.) on the Internet that are not easy to get removed, while there are other things you can (such as, deleted cached web page information).
LifeHacker has a great article on "How to Clean Up Your Online Presence and Make a Great First Impression", here is excerpt from it: "Odds are someone is searching the web for you right now, or at least has looked you up fairly recently. Do you know what they learned? Better yet, do you control the pages and profiles they visited? If not, it's time to take your online reputation into your own hands instead of leaving it to Google. Here's how." (read the rest of the article)