Motorola Mobility's CEO says Android handset manufacturers skin Android with their own UIs because the carriers demand it. Apparently it gives the illusion of a broader OS product offering than if they all ran stock Android. If this is true though, wouldn't the carriers embrace Windows Mobile phones as a truly differentiated OS choice? Apparently they aren't, because Microsoft is just launching a $200million program to pay salespeople a bounty for each Windows Mobile phone they sell, in an effort to get them to actually show the phones to prospective customers.