There are two kinds of computer owners: those that backup their data, and those who will backup after they lose something irreplaceable.

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What is most important to remember is that while a coach may excel at any number of these traits, history has shown that they certainly are not irreplaceable.

FORBES: Best College Basketball Coaches For The Money

Many of the services the environment provides, like clean water and air, are irreplaceable necessities, they point out.

ECONOMIST: A new report comes up with a better way to size up wealth