We consider the suggestion that, as a matter of caution, the deliberate broadcast of signals to the cosmos should be proscribed. We explore the likely capabilities of extraterrestrial societies that might conceivably pose a threat to our species and show that this suggestion is without merit because even if followed, it would fail to keep our existence secret. In addition, trying to limit signalling activities would be a burden on our descendants, crippling their own activities for the indefinite future. A corollary to these considerations affects the search for extraterrestrial intelligence (SETI): namely, it seems inarguable that technologically advanced beings will assume that other societies are capable of detecting their leakage. Consequently, the premise that SETI should expect to find deliberate beacons from other worlds may be mistaken.