Asymco:

As individuals we think that having lots of cash makes us rich. For companies it’s the opposite. Cash is a liability. If you come across a company that is cash rich and has nothing else, its enterprise value will be zero. Companies are valued on their future cash flows, meaning their ability to generate cash, not how much they managed to keep. In other words, cash is a measure of past success and investors are interested only in future value.

This is an excellent FAQ on Apple and the Everest-sized mountain of cash they are sitting on.