I think you have conceded my point against using Mono 
    for a startup i.e. there is a real chance you are going 
    to incur future costs of an unknown size.

And do you think that those (possible/unknown) patents that might apply to Mono cannot be used against whatever platform you're using?

Think again ... at least one of the Oracle patents (IANAL, but have been reading the independent claims) applies to any VM that starts interpreting code before doing compiling, which applies to many tracing compilers (from my understanding, LuaJIT, JavascriptCore are good examples).

You think you're safe, think again.