You could say the same thing about developing software for any platform that isn't open. None of these companies could have foreseen that Apple would drop the hammer on the creation of tools to help developers create more iPhone applications. They still have to pay Apple to develop for the iPhone. It's not like this was some end-run around the system.

Some companies are interested in having their ecosystem succeed and keep their agreements largely stable. Developing software for Microsoft is typically a solid proposition, for example; they're unlikely to change the agreement as to what toolkit you can use after the fact.

Apple, on the other hand, has shown a somewhat... avaricious... approach to the app store, rejecting applications for curvy buttons, speech bubbles, or being able to load arbitrary images from the internet. We should all realize that Apple will allow precisely what it wants to with respect to the app store, and nothing more. They don't need to do anything else; consumers will buy their products regardless of how the apps can be created.

I don't like it, but I definitely saw it coming. :/

It especially sucks if Apple does follow through with this and the people that paid for MonoTouch end up with a digital pet rock.

http://monotouch.net/Store $999 for the Enterprise version? Ouch.