The security blame in this case is not really an uneducated one. The operating system provides weak security restraints for accounts, and you're blaming the application?
Please. If you install Google Desktop Search as an admin, it will have administrative privileges. Your dream analogy with Unix would not work, because on Unix account you'd probably install it as a user, and thus it would have the same permissions as you do.
People get hung up on the idea of this application suddenly discovering everything on the hard drive, but they forget, that such activity would be possible with any similar app, whether it comes from Google or not.