I don't have it, and my auto updates are on. Guess I'm just an anomaly. I don't go out of my way to avoid Silverlight, but I haven't been prompted to install it either. Not that many sites using it yet I suppose.

The auto update would only cover Win machines anyway. Granted, there are a lot of them out there.

Guess between Flash and Silverlight you have to pick the lesser of two evils or none of the above.