The board has also authorised a $10 billion share buyback program to start in fiscal 2013, after September 1, and to be carried through over three years. This gives Apple the option to buy more stock if it wishes.
In a press release, the reason for its share repurchasing plan is to: “neutralize the impact of dilution from future employee equity grants and employee stock purchase programs
http://m.zdnet.com/blog/btl/apples-cash-plans-pay-dividend-10-billion-share-buyback/71821?tag=nl.e550
