please consider this a point of reference for the discussion and just an opinion.
regarding subject at hand.
(1) http://www.iantivirus.com/compare/ Link Regarding Todays, I anti-virus
(2) http://www.sophos.com/en-us/products/free-tools/sophos-antivirus-for-mac-home-ed ition.aspx Sophos
(3) http://www.clamxav.com Link to clamxav
In my humble opinon - people (mac users) have frowned on any norton product since the G3 macs or Osx. Many people stated that norton worked poorly on their computers and somehow used computer resoources or would wreck the computer..... So it is hard to get people to step away from this negative view. The alternative was always use Clamxav. Something you still see today. (which occasionally bothers me)
It is due to this reason. I tested several av's or the products above
(a) http://eicar.org/86-0-Intended-use.html and all of the products responded well to basic tests when active and running.
I am not a security expert and I agree with everything everyone has stated. There are also INTEGO which in my understanding is the best AV for Mac. There Is Kaspersky as another AV
I have used Intego, I have used norton for mac and once a month or so I sweep the computer with Iantivirus, Sophos and Clamxav......my base product left on the computer is Clamxav due to a lack of knowledge in the world of security, malware, java injections, browser, etc
Enclosed you may find some helpfull ways to protect yourself as well
http://www.macworld.com/article/1051426/protectmac.html
http://www.maclife.com/article/howtos/how_protect_your_mac_javabased_malware/