Allchin on AV in Vista

I have no beef with Allchin, but this seems optimistic:

During a telephone conference with reporters yesterday, outgoing Microsoft co-president Jim Allchin, while touting the new security features of Windows Vista, which was released to manufacturing yesterday, told a reporter that the system's new lockdown features are so capable and thorough that he was comfortable with his own seven-year-old son using Vista without antivirus software installed.

Link here (via realtech and Jeff Nolan).

Ok, Vista is a vastly improved security model, but what about the fact that probably well over 90% of all viruses come through email? You get an email that says “Please reset your password, open the attached file”, you open it and it’s a virus. It’s the user executing a virus. How will Vista protect against that? Furthermore, what about downloading a trojan?