Apple's upcoming iPhone operating system 3.0 will to more easily switch between App Store accounts. That could make it easier to share apps between users, though they may be required to share their passwords, too.

That feature appears to be less smooth than Windows Marketplace, which will require customers to register the phones for which apps will be shared, Bouie said.

Apps can be downloaded as many times as needed, to re-install on replacement or upgraded phones, provided users don't go over the five-phone limit, Bouie said.

Microsoft will use its LiveID authentication system for tracking. "It will be very hard for the casual, semi-casual or semi-pro user to pirate apps," Bouie said.

He disagreed that app sharing will anger the developers Microsoft needs to woo.