For one reason or another, almost all pre-modern states engaged in it to root out conspiracies, etc, and frequently with some success (e.g. Guy Fawkes). Even the US uses it - either through waterboarding, or by offshoring the really nasty stuff to friendly dictatorships - in the war on terror.
So is it actually more effective than the alternative, which is, I don't know, just asking questions without the threat of physical violence?
Obviously, this poll is only about its effectiveness. Please leave the obvious (and to most of us here valid) moral objections out of it.