Google Update is indeed very sneaky. Its installation piggybacks on plenty of Google software (including browser plugins) without telling anything and then it installs a task into Windows Scheduler that keeps respawning it when you kill it.
Oh man. I was just about to install Google Earth to play around with it, but now I'm having second thoughts. Can I opt out of the updates and installs, or is it just plain malicious?
(Yes, installing anything without my permission is malicious, even if the installed software is benign.)