What's the patent FUD, specifically? I'm not talking about some obscure part of the Winforms API, I mean in the core language itself.
Microsoft made some veiled threats a few years ago, intimating that their deal with Novell for Mono was exclusive. No one is really privy to the terms of that arrangement, but it made a lot of people really nervous.
And you forget that C++ has a giant environment to install as well, but due to age, that is generally part of the OS as is.
C++ is quite capable of operating entirely without a run-time environment. It depends only on the C++ standard library and the C standard library, which, while implemented by the OS, are completely optional.
In time, modern generation languages will end up in the same category. In fact, Windows Vista and 7 already come with .NET pre-installed, so there's no need to download anything to run a .NET app.
But this is not the case on non-Windows platforms.