Here's some interesting statements from the Silverlight 1.0 EULA:
AUTOMATIC UPDATES. This software contains an Automatic Update feature that is on by default….Unless you expressly opt out of this feature, this feature will
(a) [connect to MS]
(b) [send user info to MS]
(c) automatically download and install, or prompt you to download and/or install, current Updates to a previous version of the software.
I think the 3 options show that Silverlight is weird...Which means "Once Microsoft gets a user to install Silverlight, they have permission to silently send arbitrary updates forever after!"