Go to HR, explain that the new security policy about not running Google
Desktop is make-or-break and explain why. To achieve this you may need
higher-level management buy-in, so hopefully you can threaten exposure
under HIPAA, Sarbanes-Oxley or some such _IF_ the policy is ever
breached. Make it a matter of "if our IDS sees traffic from your
machine to desktop.google.com (or whatever) its an automatic HR
warning", and then let your standard (two, three, whatever strikes and
you're out) HR policy deal with enforcement.