i don't like flash or silverlight personally, due to them being closed platforms and not available on all OS's. i design a lot of business websites, these guys want to make money, so they want to appeal to the largest group as possible, they could careless if the person is on mac, ios, android, *bsd, linux, or windows or what browser they have, they just want the site to look good, to have form and function.
so to me, that automatically limits the use of silverlight (as moonlight is a poor implementation of it to begin with.) as silverlight only really works with windows as it is a MS competitor to flash, and flash is flaky in linux, and i don't believe ios, android nor the *bsd's have flash clients (i think i'm wrong about android not having it.)
i personally believe that websites should be platform independent, and choosing to use a propietary client side language like silverlight and flash, destroys that belief
a bit off topic, i've often wondered if google suddenly switched to a linux/android/chrome OS only client side language for google.com and services, and then banned the use of IE all together on all google.com and services, how fast would that topple MS
(i know, some dreamy linux fanboy talk
) but it makes you wonder if the shoe was on the other foot...but then again it would prolly backfire, the sale of MS office would skyrocket and bing would become the number 1 search engine and with in year ppl would prolly be like "google what?"