The problem with the Security Through Endless Warning Dialogs
school of thought is that it doesn’t work. All those earnest
warning dialogs eventually blend together into a giant “click
here to get work done” button that nobody bothers to read any
more. The operating system cries wolf so much that when a real
wolf — in the form of a virus or malware — rolls around,
you’ll mindlessly allow it access to whatever it wants, just out
Mac OS X does a really, really good job balancing security and convenience; it sounds like with Vista, Windows is overcompensating and veering from “too convenient” to “too annoying”.