John Maynard Keynes, the economist, argued that companies tend to hoard cash for three reasons: to perform day-to-day transactions, to protect themselves in the event business slows, and to prepare to make investments should opportunity arise.
Apple certainly isn't using its cash for acquisitions. Compared to its competitors, the company spends very little money buying technologies new or old.
Google has spent billions on video sites, robots, driverless-car technology and artificial intelligence software. Amazon has bought robot makers, e-commerce services and hardware start-ups. And Facebook has spent more than $20 billion in just the last two months on a messaging platform and virtual reality technology.
Internal Apple document shows worries iPhone growth could stall
Yet Apple has barely broken the skin over the last decade, buying AuthenTec, a fingerprint sensor company; Siri, the voice service; and Topsy, a data analytics company.
Apple has never even made a single acquisition over a billion dollars. Where are the robots, the driverless cars, the virtual reality goggles?
In an interview in February with The Wall Street Journal, Timothy D. Cook, Apple's chief executive, said the company had looked at big companies but had no urge to buy for the sake of buying.
"The money is also not burning a hole in our pocket where we say let's make a list of 10 and pick the best one," Mr. Cook said. He said Apple was "not going to go out and buy something for the purposes of just being big."
But the money is burning a hole in the pockets of investors who want Apple to use some of its cash to pay dividends, buy back stock or both. Carl Icahn, the vocal billionaire investor, is leading the charge.
Microsoft unveils voice assistant Cortana to rival Apple's Siri
Rick Lane, an analyst with Moody's who wrote the report on the company's cash holdings, said Apple could be holding onto some of its cash for a rainy day. Apple once fell on "very difficult times," he said, "and had to rely on, in part, the kindness of others."
"Without having to rely on the capital markets, which can be mercurial, it's a kind of self-insurance to have that cash on hand for the times when things go bump in the night," he said.
So what could Apple buy with its miles of cash?
Compared to Google, Apple seems to be focused on the here and now rather than the far-off future. (Google is building autonomous robots and cars.)
Apple could leapfrog its competitors and go all in, picking up Mars. (Yes, the planet.) NASA scientists recently said a human mission to Mars with the goal of building a colony would cost about $160 billion. NASA even floated the idea that big corporations could sponsor the trip.