The new Facebook Terms of Use includes the following paragraph:
You hereby grant Facebook an irrevocable, perpetual, non-exclusive, transferable, fully paid, worldwide license (with the right to sublicense) to (a) use, copy, publish, stream, store, retain, publicly perform or display, transmit, scan, reformat, modify, edit, frame, translate, excerpt, adapt, create derivative works and distribute (through multiple tiers), any User Content you (i) Post on or in connection with the Facebook Service or the promotion thereof subject only to your privacy settings or (ii) enable a user to Post, including by offering a Share Link on your website and (b) to use your name, likeness and image for any purpose, including commercial or advertising, each of (a) and (b) on or in connection with the Facebook Service or the promotion thereof.
Crucially, the recent change removes the following paragraph from the Terms of Use:
You may remove your User Content from the Site at any time. If you choose to remove your User Content, the license granted above will automatically expire, however you acknowledge that the Company may retain archived copies of your User Content.
Link: 'Facebook's New Terms Of Service: "We Can Do Anything We Want With Your Content. Forever."', The Consumerist, Feb 15 2009
You can delete, rather than simply 'deactivate', your Facebook using the following URL: http://www.facebook.com/help/contact.php?show_form=delete_account
UPDATE: They've backed down on this. New terms of use will be drawn up soon. Keep watching the skies tubes.