Facebook is a very ingenious business model with the capture of a global network of IP at its heart.  For reference to this see the almost unfathomably bold terms on the site regarding posted user content ... "By posting User Content to any part of the Site, you automatically grant, and you represent and warrant that you have the right to grant, to the Company an irrevocable, perpetual, non-exclusive, transferable, fully paid, worldwide license (with the right to sublicense) to use, copy, publicly perform, publicly display, reformat, translate, excerpt (in whole or in part) and distribute such User Content for any purpose on or in connection with the Site or the promotion thereof, to prepare derivative works of, or incorporate into other works, such User Content, and to grant and authorize sublicenses of the foregoing."

Interestingly it also used to be that if you deleted your facebook account your information was also deleted but in recent weeks that changed and was reflected in a change in the terms and conditions of site use from:
"If you choose to remove your Member Content, the license granted above will automatically expire." (from Wayback Machine)  to the current:
"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."