Apple Inc. has recently come under attack for its practice of stockpiling cash. At the end of last year, the company was sitting on $137 billion — and the heap keeps growing.

Corporations normally don’t hoard cash the way Apple does. They keep enough around for immediate needs, and either invest the rest in their operations or dole it out to shareholders in the form of dividends or stock buybacks. If they need more cash for, say, an acquisition, they borrow it.