So, you decided to go with the flow and get into social networks, blogs, and forums. You've signed up for every new site, and you've posted on every interesting forum you could find. You've got videos on YouTube, photos on Flickr, and your latest quip about the economy in your FaceBook notes.
Whatever the reason, it's become apparent that you want to completely eradicate your online presence. You want to effectively no longer exist on the internet. With all the online accounts you may have signed up for at any given time, this could be quite the monumental task.
The first step in erasing your online identity is to keep a listing of all the sites you've signed up for and those usernames and passwords. People will sign up for a website and then forget about them as the initial curiosity fades. However, this doesn't mean the website forgets about you and all the information you may have entered. Keep a physical list of all websites and accounts you've created, so when you do want to clean up your web identity you know where to start.
For information on cleaning up and deleting specific website accounts check out this PCMag article: http://www.pcmag.com/article2/0,2817,2342599,00.asp
If you are concerned about other personal information that has been gathered by search engine crawlers or your information has been erroneously added to a website and you have no means of getting it off said website, you may have to look to other alternatives. http://smashgods.com/2008/08/20/become-web-dead-erase-your-online-identity-in-10-steps/