Users who access our SharePoint sites must log on to our network. We
do not allow anonymous users. We add users to our sites via the
Exchange address book (Active Directory). All of our users are
authenticated and we know their identities.

So, if Ima Workerbee creates something in a site, it shows up as
created by "Ima Workerbee." If she turns on Alerts, those alerts will
go to her email address, Ima.Workerbee@....

But, she can go to the Update My Information screen, and manually
change his name and email address to anything he likes, such as Big
Boss and Big.Boss@... respectively. Now if Ima creates
something, it will show up as created by "Big Boss." If Ima turns on
Alerts, those alerts will go to Big.Boss@....

Isn't that a huge security problem? Is there some easy way to turn
off a user's ability to change their name and email address?