Silverlight is better if it is used less. Flash solved a problem that is now much less of a problem, so it is better if it is used less too.

\MS bringing silverlight in to "compete" with flash was a stroke of misguided stupidity. It just makes matters worse.

Don't install it, don't use it, and it will go away. Take the time to email sites using and let them know they have made a bit of an error.