It looks like BBs T&Cs are worse than Facebooks – the latter say “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.” which at least means that if they have lost their backup, they no longer lay claim to the material. At least, within my interpretation of what an expired perpetual license might mean, anyway!
Interestingly, Facebook’s agreement actually means you cannot post non-commercial creative commons content there.
Thanks for the shout-out by the way 😉