Or per a single user, even if all else works well: - Email account gets hacked, and you can't respond to emails anymore. - Spam filter bug filters the service

Or per a single user, even if all else works well: - Email account gets hacked, and you can't respond to emails anymore. - Spam filter bug filters the service's emails for 3 consecutive weeks. - You are simply hospitalized for a few weeks, maybe under anesthesia, maybe in a temporary coma, maybe some memory loss. A "dead man switch" needs to be more robust for really sensitive stuff IMO.