I agree, as a Chem Eng master (In the dutch system you do not leave university with a bachelor, it's interpreted as if you weren't good enough to get a master) I've noticed that most of the guys I considered to be the brightest left for corporate jobs, that Ph.D's were a mix of people with deep academic interest (and endurance), some very bright people, and some people that felt they weren't ready for the real world. I think it's too much of a short-cut to say PhD equals high intellectual success.