With Windows Phone 7, you don't look for Apps anymore

Very apt and very true. With Windows Phone 7, you don't look for Apps anymore. Since day one of Windows Phone 7 release, Facebook has had the best integration of all phones in Windows Phone 7 and with Mango, Twitter, barcode (including Microsoft Tag/WR codes) reader, shazam kind integration are also an integral part of the Phone. I am assuming that any ecosystem which extends API should be easy to integrate with Windows Phone 7 once they license the API usage to Microsoft. Once you license the API usage and WP7 integrates your app, it is a big win for the app maker. You now are a default in all the phones that Microsoft sells and you don't have to advertise anymore to be downloaded. 

HTC boss on Windows Phone 7, patent wars and why iPhones aren’t cool anymore

On the release of the Windows Phone HTC Titan: “I am very happy about these phones, because the integration of Windows is just beautiful. Integration of Facebook, Twitter, everything works seamlessly. It is hard to describe, but you don’t look for applications anymore, you just think about who you want to communicate to and the channels become obvious.”