Facebook claims rights over the photos you upload on the site! Rights like worldwide license to use for instance.
"For content that is covered by intellectual property rights, like
photos and videos ("IP content"), you specifically give us the
following permission, subject to your privacy and application settings:
you grant us a non-exclusive, transferable, sub-licensable, royalty-free, worldwide license to use any content that you post on or in connection with Facebook ("IP License"). 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."
Statement of Rights and Responsibilities