Wow. That would definitely get annoying after about 2 weeks.
Most users never even notice it. The weekly reload happens after hours, so those who maintain a relatively "stock" configuration don't see any difference.
This setup simply forces users to look at the real neccesity of the software they are installing. If it's vital to their job, they'll get sick of reinstalling and have it added to the image (allowing the software to be vetted). If it's not vital to their job, they'll get tired of reinstalling and cease putting these sorts of things on. Either way, the company wins.
If users are getting annoyed because their email smiley software keeps getting blown away every week, that's a GOOD thing.