Big free software wig, Richard Stallman, has weighed in on the Mono issue in Linux, saying why we shouldn’t depend on applications written in C#.
The problem is not in the C# implementations, but rather in Tomboy and other applications written in C#. If we lose the use of C#, we will lose them too. That doesn’t make them unethical, but it means that writing them and using them is taking a gratuitous risk.
If you haven’t already, have a read of my creative commons article on Mono.