I can definitely understand your curiosity and I've even contemplated why the technologies covered in Wireless# are the technologies covered.
One common thread that I noticed about all the technologies in the Wireless# objectives is that they can be implemented without license. Excepting, of course, WiMAX until/unless we actually do see some license-free WiMAX implementations.
IrDA, RFID, WiFi, Bluetooth, ZigBee - they all use license free frequencies/technologies. WiMAX can according to the standard, we'll have to see.
Has anyone else noticed any threads that weave through the technologies currently covered in Wireless#?