Microsoft Silverlight was to have many functions upon release, but was not ever widely accepted with web developers, so there aren't many sites that utilize it in any fashion. The only site I know of that uses Silverlight is Netflix.com for streaming movies.

What Le0n_X alredy hinted, I would be more direct: there are many reasons NOT to install Silverlight, among them:

(1) Fewer quirky plug-ins keeps your system or browser more stable and secure.
(2) Proprietary technology which means it excludes development and (partially) adoption by others, besides being against what made the web successful: open, generally accepted standards.
(3) Probably as a consequence, not widely used or accepted.

I discovered after my post on this website that Kelley Bluebook is supposed to use Silverlight. So I tried the link provided in a Silverlight promotion for the software. So far, from what I can tell, there is nothing at KBB that indicates they are using this software for those shopping for vehicles, despite the extensive claims of KBB developers. Maybe if I get further into it I'll learn more, but at this point it looks like "vaporware". It looks as if I might be closing in on the "Add/Remove Programs" window.

You can always disable the Silverlight plugin via "Tools > Add-ons > Plugins" and only enable it if you encounter a website that uses Silverlight and you want to allow that plugin. I do this with Java as Java can have security issues and there is usually no need to have Java enabled all the time. There is no restart required after enabling or disabling a plugin via Tools > Add-ons > Plugins.

Thank you for your suggestion, Corel,

I've already removed the Silverlight program. I feel that Kelley BB and the Silverlight developer on the Silverlight web site that were promoting Silverlight were not being honest about the software. When somebody is not being honest about something there's no telling what other untrustworthy things they may be doing that are reflected in their software.