I have this theory: Unix actually died of chronic obsolescence in the late 70's, but was raised from the dead in a vile demonic pact. Sure, you can throw hand grenades at Unix, but when the smoke clears, all the little parts will still be twitching. In an hour or two, Unix will reassemble itself, and start shuffling towards you again with that blank zombie stare. (And in today's cutthroat operating system market, being undead is probably a survival trait.)