It appears it has begun. With the growth of Macs, Windows viruses and Trojans are being ported to Macs. Looks like the Mac users days without worry are about to start coming to an end. It was expected though. The larger the target, the more appealing to attackers. Mac users always thought MacOS was just safer. It just has less surface area to attack. (amount of users) Apple knows those days are coming to and end too. At least they are starting to do something about it. Of course all the other OSes (including Windows) have been doing this for quite some time. OSX is just catching up to the party in both categories.