yeah thats a good question... how much of this is zune HD. at some level though does it matter? if its easy for developers to kindof plug into the whole social networking/application platform... maybe its just some stripped down OS e.g. the zune HD plus thier social data hub.. and maybe thats all you need right..
we have been moving away from needed full blown operating systems on anything except servers in datacenters.
the iphone OS is real stripped down right .. noting like the pocketPC OSs but they gave what the customer needed
the early windows phones failed cause theres was too much OS and not enough of anything else.