Of course the whole point is that while any windows machine without the update or a proper firewall could be infected. Meanwhile, a Mac OS X (and probably everything else Unix) machine comes with a firewall and all ports turned off. Your computer has to start a connection with someone else to get traffic on almost any given port. And I guess that it might be hard to browse the internet on the 16th because of the massive DoS attack on the update site. But still, if anyone has a windows 2000 or xp machine, leave it on for that one day.