1. You're only learning so much. If you're a great young guard (Augustin, for example), you're playing mostly with guys who aren't especially great and are just trying to impress scouts. There's not much of a team atmosphere, from what I've seen.
2. Many people do great at the camp and then are never heard from again. I don't know what this means, but I do know that there is no correlation between great play in camp and quality play in the NBA.
3. Everybody is playing less time against other marginal talent. Can you really evaluate talent under those conditions?
Don't get me wrong; I see the benefit of watching guys play in game conditions against fresh opponents. However, I don't see much going on with these camps that translates to success in the NBA, other than a better idea of who to give the 14th and 15th spots to, who you will eventually wave.