I don't think torturing should be exercised at all. Isn't there some kind of mind-altering substance out there that could inhibit the person's... inhibitions and just make him answer every question without really thinking about it? Hell, you could probably do it with a generous dose of alcohol. I just don't see how torture can be effective especially when there's no guarantee that the person has the information you're looking for and that what he's telling you is definitely true (especially when what he thinks is true may not be the truth).
Although, that's just torturing for information. If your purposes are different - say if you just want to make POW No. 454 behave himself - then maybe it is effective, though I'm not saying it's therefore right.