"including its billions of encrypted, peer-to-peer Internet conversations." And why on earth would Skype need to keep the conversations on a backup tape long a

"including its billions of encrypted, peer-to-peer Internet conversations." And why on earth would Skype need to keep the conversations on a backup tape long after the conversation is over? Shouldn't they be erased from everywhere (Skype and peer-to-peer hosts) once the call is ended?