Here are some comments received from readers on puzzles in my brainteaser book:
On the "Completely surrounded" puzzle:
Mike Shulman pointed out that many places along the border between Mississippi and Arkansas satisfy the condition in the puzzle, as the border follows the meandering path of the Mississippi River. Jeff Maddrey found a place in the northwest corner of Staten Island that works. The whole island has New Jersey to the north, west and south, and a tiny part of the far northwest corner also has a piece of New Jersey due east.
Jeff Maddrey also observed that the solution to the camel crossing the desert puzzle doesn't prove that the solution can't be improved by having smaller intermediate piles. Some additional explanation is now provided on the Brainteaser Docs page.