Cary:
This is verging on the Matt Ward theory of golf courses -- that is, courses aren't ever too penal, it's just that golfers are too dumb to play from the correct tees.
I never play from the tips, and always play from tees that suit my barely mediocre game. And I still find some courses (like Blackwolf Run) overly penal, while finding much enjoyment out of others (Lawsonia Links) that provide challenge without exacting punishment that's over the top.
Bah, guys like cary and Matt who I would guess hit it mostly straight always assume this. There are plenty of us who are easily long enough to play from the tips anywhere who would be overwhelmed by a tight course from the ladies' tees on a day when the 'ol swing timing's way off
I think that a lot of what makes a course penal, as well as what makes a course great, is in the eyes of the beholder. I know there are plenty of people who don't even think Carnoustie is great, so it couldn't be an example of a penal course for them. I consider it great, but don't consider it particularly penal, but then I've been quite successful there so maybe it just fits my game somehow. Though, on the other hand, I'd consider Muirfield quite penal (as well as great) but I had a terrific ball striking day there and played quite well, so I make that assessment based on knowing how awful my day could have been if I had happened to have visited there on a day when my ball striking was off.
Guess it depends somewhat on the definition of penal, which to me simply means there are plenty of places where a bad shot results in the loss of more than one stroke, either due to a stroke and distance penalty, or a situation where it is very unlikely you'll be able to get yourself back to where you ought to have been with a decent shot in the first place.
Theoretically, a course with wacky enough sidehill lies or where angles were important enough could do this to you with 100 yard wide fairways, but even at TOC I don't believe this is really the case. That is, I ain't never seen it happen from "bad" places in the fairway on any course other than maybe a handful of holes, those wishing to prove me wrong are free to invite me to an example of their choosing! So in practice I think it takes penalty strokes, trees or deep rough to make a penal course, but I'd love to be proven wrong about that.