Alot has been written about how hard it is to really get rid of your facebook life should you so want to (just google — lol), but facebook does say that you can do it in one shot, which this fb group explains. Deleting an account is supposed to scrub facebook of all of your posts, comments, tags, your virtual footprints… You can go directly to the link, here.
Of course, you can always manually delete each tag, post, video, photo, comment,etc. (which was the original way to do it, and then your account just moved to inactive at some point); but deleting your account (in theory) should scrub the site.
Facebook is now taking legal action against them. The thing with fb is that it is a COMPANY building a huge db of consumer info, which is an obvious minefield for privacy issues, both from 3rd party access (games, quizzes, linked accounts to other services like twitter, etc.).
The short answer is: WATCH YOUR BACK. The information you are giving out to a company (not just facebook, but any company including google) is not only available on the web, but on their servers, and anywhere else they store your data. Just because you might be able to delete info from a publicly available website, does not mean that it still does not exist, either in a backup file or in a cache somewhere.