Some (Danny Sullivan, Tom Spring) are raising legitimate concerns over privacy and security issues with Google Desktop Search.
Curious, though, that these concerns are only coming up now. Google is not the first to do desktop search. There's Hotbot/Lycos, Blinkx, X1, Copernic, Enfish, dtSearch, MSN (Lookout), Ask Jeeves (Tukaroo), and many others. Like the GMail privacy flap, Google seems to be held to a higher standard.