It's not just about the respective sizes of the platforms.
Novell has had a rude awakening with the future of MonoTouch being up in the air. With the recent changes, Apple has made the viability of that product uncertain. While Apple hasn't thrown out C# apps so far, they haven't green lighted the approach either and probably never will. MonoTouch is only available for the iPhone ecosystem, is already supporting iPhone 4, and Novell has made it clear that it will support any and all enhancements to the API in the future, but I doubt that will appease Apple.
Anyone developing for the iPhone would run a considerable risk using MonoTouch. There is a strong possibility that Novell will look elsewhere (Android) if the revenue dries up. In fact, they already are (MonoDroid).
This is not only Novell. Any toolmaker or middleware creator should think twice before entering the iPhone market.
I believe that a healthy ecosystem is important for the succes of a platform. Apple apparently disagrees. Whether it is the deciding factor causing the stagnation of the iPhone platform is uncertain. It will definitely be interesting to follow in the next couple of years.