You've done the hard work of pegging a pitcher's tell - does he tilt his glove a certain way when throwing his curveball? Or, through keen observation, discovered that a catcher is sloppy setting up behind the plate and you can see what pitch he's calling for next.
Baseball's unwritten rules say it's OK to exploit this intel. After all, as Rich Donnelly, the longtime MLB third-base coach put it, "If they're stealing your signs, then your signs aren't good enough."
But turning to electronics or cameras in the quest for an in-the-moment edge? Or being so overt when delivering the information by, say, whistling so loud the other dugout notices?
That's where the romance of sign-stealing ends and hard feelings begin.