Here's a random question that popped into my head after reading @Kai "the spy"'s posts.
How long do radio signals, and the other signals they use to search for extraterrestrial move? Could there be life out there sending signals right now, but we don't know because all of the signals we're detecting are ancient? Or the other around, if we do detect a distant signal, would whoever have sent probably died out a long time ago?
Morality: The interstellar post office is no better than our own...