Who in the world wants to help Microsoft take over the World Wide Web? Why, so they can shut everyone not using Windows out once they have the penetration they want?
Mono in general is a retardedly stupid idea, and the more it penetrates Gnome, the more dangerous Microsoft becomes to the Gnome project in general. Not to mention Flash works just as well, and don't start with the "Mono is open-source!" counter, because it's not. Sure you can get the source, but then you put yourself at risk of being sued by Microsoft for patent infringement. And the idea they won't is stupid.