To do a bigger stock buy back, Apple needs to go into debt to finance it because it does not really have access to the 150 billion dollars in cash every one keeps talking about.
Every one keeps talking about how much money Apple has but they are leaving out the most important point.
Most of the money is not in the US. To bring it back will incur huge losses because of taxes.
What happens when the economy turns ugly and Apple is in debt with no quick access to cash...