Camps are used for many purposes, from the opportunity to make money, to provide instruction, etc. Certainly though coaches want the chance to see you and if this is a chance to be seen I don't see where there's anything to lose.
Are they primary recruiting tools-typically not. But, again, if you are interested in a specific school and they have a HS age camp I'd say go. If memory serves, I believ that Harvard and Yale have camps. Not sure about the others and like I said in the last post, Stanford has a camp each summer where typically 30+ schools are present and typically all of the Ivies are there.