To delete your Facebook account simply point your browser to https://www.facebook.com/help/delete_account
P.S. Kudos to Facebook on the great job hiding the ‘Delete Account‘! In Settings you will find only the option to ‘Deactivate’ your account.
P.P.S Kudos to Facebook on the great job on SEO-ing Google, Google’s Help Box points the User to Deactivate, instead of Delete.
P.P.P.S Kudos to Bing for providing the correct Help Box (although for some reason we are not able to trigger the Help Box any more)