They are removing the number of shares on the open markets, so it's a 'less to go around' type sitation, or you can think of it as limiting supply.

In theory (I believe), the market cap for the company should stay the same, so each share increases in value. Cook and Icahn are major share holders, so they would be increasing their value.

However, it isn't a zero-sum game (hope I'm using that correctly) as in the short term, with rising stock price, all investors win.

On the flip side, the money used for a buy-back is money not invested into R&D, which for a tech company is obviously very important.

Though, I wonder if Apple may be a bit of an anomaly. They have such a huge profit margin, and strong following, and a group of customers who will buy pretty much anything they release at pretty much any (moderately unreasonable) price.

Apple doesn't spend (and loose) on R&D like Google and Microsoft do. There doesn't appear to be anything in the Apple quiver which came as a result of massive R&D effort. Massive design effort, absolutely. Massive engineering effort, sure. But straight R&D? I don't think so. Happy to be proven wrong though.

Tim Cook borrows $150B and uses it to buy Apple stock. This shifts the demand curve for Apple stock out (to the right). The equilibrium price of Apple stock rises. Tim Cook sells his stock at the new higher price. He profits.

More likely Joe Schmoe's pension plan will see Apple's stock go up and buy more shares, thinking there's real market demand for it. But there isn't. This is really just a variation on the classic "pump and dump" scheme.

Worst case scenario: Apple does this three or four more times, can't service its debt, and gets driven into bankruptcy. Then Joe Schmoe's Apple shares in his 401k are worth $0.