At work we use the norton anti virus stuff on OS X, and I don't blame them because it is a heavily networked enviroment with semi-anonymous and untrustworhty users using any computer they please at random, but I don't really think that viruses are really a threat to OS X, but of course that won't stop magazines and anti-virus companies from telling you need them or selling them. (example: You here at Expensive Ads and MS Propaganda magazine I heard that many OS X users are lazy when it comes to virus protection. So I talked to Steve; hes the virus super security genius intellegent know-hell-of-alot-more that you/sales representative guy from Acme Anti-virus. So I asked Steve if viruses are realy not a problem for OS X or Unix? WOW,Steves says you are a moron not buy his product and hackers will take over the planet if you don't install his program right now! Here's a link to their website!) 😛
But then again if your worried about it though, I would not ever think down on someone or think it's stupid to install any extra security on a computer. Better safe than sorry.
As long as you play it smart you'll never have to worry about it, and even if you do get a good anti-virus software that won't do anything to protect your computer if you are stupid about things. Most of the updates you'd get every month are mostly (I'm guessing) for windows macro viruses that get sent along with windows documents and email attatchments, which realy isn't even a threat to you. But then again it may stop you from accidently spreading a virus in a document you received from a windows user to another windows user, so it may be a good idea out of simple common courtesy.
You know there are about a hundred or so known viruses for Linux, of those only a few were dangeous, and almost none of them have any chance in a computer that is properly updated. In linux land when a new virus/hack is detected they figure out the problem and fix it. (were as MS solution is to deny the problem blame it on hackers and make you buy third party bloatware that screws up your email) Security updates are probably enough for OS X. Poor windows users have to deal with 660,000 plus known viruses, but I am sure XP is perfect enough to protect them. And if there are any new Linux viruses, they are currently unkown and no anti-virus stuff in existance will stop a new unknown virus... And I would suspect strongly that OS X is in the same boat... Most virus you would have to worry about would only affect the classic mode 'cus they are old 9 OS viruses and viruses design for OS X versions of microsoft software like outlook.
A good thing I suppose for OS X users, if there were any realy dangerous viruses I'm sure just paying attention to Macs forums would alert you to any problem.
The old MS excuse is that well Linux and Macs haven't been around as long and ain't as popular. But soon hackers will go after Linux/Mac because they will get more of a thrill. SOMEDAY! Ha haha. Basicely MS OS's are a security threat just by installing them into a computer. Since MS is so unresponsive at actually fixing problems viruses get replicated. Anti-virus software can only detect virus's that are known, once a security breach is realized (like being able to install complete programs by double clicking on a e-mail attachments! OMG) its just a matter of repeating a pattern, pretty soon you'll have hundreds of different virus's all attacking the same vunerability: they just copy off of each other and change it just enough so that it can't be detected. And thus anti-virus software people get rich and MS techs blames the users for the problems.