Here’s the relevant statements in the Facebook Terms:
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You grant us a non-exclusive, transferable, sub-licensable, royalty-free, worldwide license to use any IP content that you post on or in connection with Facebook.
Non-exclusive: When you upload a photo or post a status update, you are giving Facebook the right to use it, but not exclusively Facebook. You can relicense the content elsewhere (upload it to Flickr, sell it, make posters, whatever). A non-exclusive license is a copyright license whereby the ownership is retained in full by the content creator or current license holder. This is standard practice for web services, and they legally need a license in order to store your content.
Royalty free: Facebook do not have to pay royalty charges in order to store your content or make it available to you or others.
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This IP License ends when you delete your IP content or your account unless your content has been shared with others, and they have not deleted it.
Once you delete your photo, Facebook no longer have the right to use it. They must purge it from their data stores. If you post a photo or comment on someone else’s wall, for example, Facebook retain the right to use it until either you or they delete it.
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When you delete IP content, it is deleted in a manner similar to emptying the recycle bin on a computer. However, you understand that removed content may persist in backup copies for a reasonable period of time (but will not be available to others).
Your data may persist in backups that other Facebook users cannot access for a period of time, until those backups are deleted.