For a long time, I’ve had a note to myself saying I should write about witch-hunts. And now, as the clock ticks toward Halloween, is the perfect time to do so. My status as a native and lifelong resident of Salem, Massachusetts means I know a fair amount about the historical kind, and my decades observing and analyzing the behavior of investors, who can act rational as individuals but who combine to form irrational crowds, means I’ve experienced many of the modern kind.