Eric Schmidt says the practices are zero sum. In my opinion this is exactly correct. If all the big companies just move each other's employees around, nobody benefits. If instead they all agree to look outside of the talent that's already been recruited, everyone (including developers) benefits. New talent keeps coming in, and developers not in big tech companies have a shot at working at places their parents will recognize.
1. http://pando.com/2014/03/22/revealed-apple-and-googles-wage-...