Ghosts in the machine

Cambridge University researchers have recently completed a study/experiment on deleting photos from various SNS or blogging sites, with mixed success. Whereas the picture cannot be seen any more on your Faceboo/Bebo/MySpace/LiveJournal, it would seem that in the depths of some server somewhere, your photos live their ghostly lives in limbo. If you need something more scientific than "ghostly lives in limbo", the very technical explanation is here.