Apple Inc (AAPL)

[Bootz]

Cook's sale appears to be tax related.

From AppleInsider:

Cook's shares vested last Saturday after a two year waiting period. In March 2010, the executive was awarded 75,000 restricted stock units "in recognition of his outstanding performance in assuming the day-to-day operations" of Apple while Jobs was on medical leave to recover from a liver transplant. When the first half of the shares vested last March, Cook immediately sold off the batch, netting $7.02 million after taxes.

This year, Cook's tax bill for the second half of the shares came out to $9.44 million. He opted to pay by surrendering 17,322 shares at a stock price of $545.17.