Are internal within a single organization - and I wonder how many large organizations actually enforce them - being that they must realize that they're abused. It seems like a well oiled corporation realizes that these lists are just as likely to exclude workers who would be an asset as to exclude workers who would genuinely be a problem for the org. Maybe I'm wrong though.

The problem with THIS case is it spans different corporations and industries. If Intel (a component manufacturer) is in an agreement with Apple (a software vendor and hardware design firm) to not poach employees - you've got a very real problem for the free-market employment pool.