Privacy concerns surrounding Facebook have been well documented, but you may have other reasons for wanting to walk away from the social network. Perhaps you don't find it all that useful, or you've gotten one too many FarmVille requests. If this sounds like you, you might consider deactivating or outright deleting your Facebook account.
Deactivate your account
Deactivating your Facebook account puts it on hiatus: Your profile will be removed from the site as will most of what you posted to Facebook (things like messages will stick around, however), but Facebook will retain your data in case you decide to come back. You can always reactivate your account later by logging in to Facebook.
To deactivate your account, log in to Facebook, then select the settings menu in the upper right corner (represented by a gear icon). Select Account Settings from the menu, and then on the next screen, select Security from the list along the left side of the window.
Once there, select Deactivate your account toward the bottom of the page. Facebook will try to guilt you into staying by showing you photos of your Facebook friends, and then ask you why you want to deactivate your account. Once you tell Facebook why you don't you don't want to be friends any more, click the Confirm button, and Facebook will proceed to deactivate your account.
Kill your account altogether
Deleting your account, on the other hand, kills it completely: You won't be able to log back in to retrieve or view anything you've posted to Facebook, and if you want to use Facebook again, you would have to start from scratch.
Facebook recommends that you download a copy of the data you're published to the site before you delete your account. Open the settings menu on Facebook while logged in to your account by clicking on the gear icon in the upper left. Next, select Account Settings, and on the General Account Settings page, look for Download a copy of your Facebook data and click the link. This will guide you through the process of downloading an archive of all your Facebook data.
The company doesn't make it immediately obvious as to how to delete your Facebook account, but to do so, log in to Facebook with your account, then visit Facebook's account deletion form to carry out the process.
Keep in mind: Once your Facebook account is gone, it's gone, so you should only delete your account if you're really, really sure that you won't use Facebook again.