that the sale cuts his stake in Microsoft by about 12 percent, and that if he sold a total of 75 million by year's end, it would mean a reduction of 18 percent.

To squash rumors that the sale has anything to do with Ballmer leaving Microsoft, he released a statement which said:

"Even though this is a personal financial matter, I want to be clear about this to avoid any confusion. I am excited about our new products and the potential for our technology to change people's lives, and I remain fully committed to Microsoft and its success."

But when you're head of a company whose stock price has been stagnant for a decade, and there have been rumblings from those who want you to leave, it's inevitable that people will wonder about the timing of the sale.

Ballmer hasn't sold Microsoft stock in seven years, and the sale came just days before , which could be a make-or-break product launch. The future is clearly mobile, and given the success of both the iPhone and Android phones, this may be Microsoft's last chance in that market.