In an article, IDC, noted that the Windows Phone 7 marketplace grew faster than Android. The report noted that Microsoft added 4,000 applications in just two months, a milestone that took Android's marketplace over five months to achieve.
The reason, according to "Engadget points out, there're already thousands of developers who know the programming language, which means they can quickly turn code into an app without much trial and error. The same can't be said for Android, which required Java programmers to learn new libraries and constructs.
You also need to include the fact that there're more programmers looking to cash in on the rapidly expanding mobile app market. Programmers are also porting over their apps from iOS and the Android market to WinP7, expanding their portfolio to multiple platforms."
Microsoft could easily become the third largest mobile app market by the middle of next year, which doesn't face very much competition in terms of WebOS, BlackBerry OS and Symbian.