Fact checking and critical thinking...
"In the PC world, Silverlight can talk to PowerPC in addition to x86 to run on Windows and Linux."
To my fellow commenter, Mary Jo Foley claimed last year to have seen a Microsoft coded implementation of Silverlight 3 running on Moblin Linux, for whatever it's worth. Also, I find the Moonlight team to be entirely reasonable, not railing against the Silverlight team, unlike yourself. Strange when people claiming to be advocates of a cause attack persons or causes that those they are 'defending' never would.
Separately, to the people whose lamentable comments I am forced to read all over the internet about how HTML5 makes Silverlight irrelevant, I must say that I find it difficult to believe that you are very clever even when you are sober. Seriously. You think that a markup language and its friend the kiddy scripting language provide any competition against a framework which allows real coders to write real computer code? Sheer idiocy, I tell you.
HTML unquestionably has massive importance, but to say that it will wipe out software designed to write real programs for the web is naive to say the least.
Plugins exist because web standards have repeatedly shown that they refuse to accomplish what is possible to be accomplished in the current day and always lag over a decade behind current computing practices. Some of us want more of what's possible right here and now and we will simply never accept progress always being dragged down by the lowest common denominator (web standards).
Standards are by no means a bad thing, but by allowing people from all sides of the argument on any given standard group (a good thing for a balanced standard) they, by definition, doom themselves to a long drawn out bureaucratic deliberation. Plugin makers, by contrast, are generally made by private companies who must provide fast, effective, long-sighted solutions or lose out to competitors, providing end users with a rapidly improving experience with quickly proliferating capabilities.