Why Mac, PPC & Linux? Well .....
Several Years back a prototype cruiser set sail for testing. It was completely computerized to lower the number of personel that had to be on board to fight the ship in case of an emergency sortee. It was running Windows NT.
In the middle of battle drills the ship went dead in the water. Someone entered a wrong number and the system freaked. The ship was towed back to port.
Needless to say the Pentagon was not happy.
True Story! :-D