@resumer You're still going to have the federated copies lying around. Anyone anywhere can store copies and none of us can (or should be able to) delete stuff from another person's harddrive.
I don't see anyone requesting the ability to remotely delete e-mails from another user's inbox, a submission to the the "opinions" part of a local newspaper or stuff like that so why _public_, federated notices?
The internet never forgets, so think before you act. Use pseudonyms. Change identity once in a while and bring only those you care about with you.