I just watched a news conference with Aron Ralston. Apparently the guy is not only an experienced outdoorsman but a SAR tech as well. His failure to file a flight plan was an oversight of a practice he normally follows. He was only carrying water for the day. He started out with 3L and was down to about 1L by the time he became trapped in midafternoon. His only knife was a cheap Leatherman knockoff. As he put it, the kind you get for free when you buy a $15 flashlight. Just goes to show, experience is next to useless if you're not going to apply it.
On a related thread someone wondered how he cut through the bone. He made several false starts at cutting his arm off but couldn't get through the bone. Seems he finally torqued his arm one way to break the radius and another way to break the ulna then cut the soft tissue free.

Ed