If you’re worried about who can see you and what they can see, remember that you have complete control over this and can edit your settings as you see fit from the Privacy page. If you still want to leave Facebook, you can deactivate your account from the “Settings” tab on the Account page.
Deactivation will completely remove your profile and all associated content on your account from Facebook. In addition, users will not be able to search for you or view any of your information. If you reactivate your account, your profile will be restored in its entirety (friends, photos, interests, etc.).
[advt]If you deactivate your account from the “Deactivate Account” section on the Account page, your profile and all information associated with it are immediately made inaccessible to other Facebook users. What this means is that you effectively disappear from the Facebook service.
However, facebook do save your profile information (friends, photos, interests, etc.), so if you want to reactivate at some point, your account will look just the way it did when you deactivated. Many users deactivate their accounts for temporary reasons and expect their information to be there when they return to the service.
If you do not think you will use Facebook again and would like your account deleted, facebook can take care of this for you. Keep in mind that you will not be able to reactivate your account or retrieve any of the content or information you have added. If you would like your account deleted, please contact facebook using this form and confirm your request.[source]