Summary
Microsoft chose wireless protocols that have point-to-point over broadcasting and one-to-many protocol propagation techniques. The biggest advantage of going with point-to-point protocols is security in addition to the capability that Microsoft will have to bring their implementation of TCP/IP into wireless applications more seamlessly. One could argue that with DHCP it really doesn't matter which is used, yet the point-to-point characteristics of IrDA and 802.11b make them the most secure.