earley, that's a great question with differing opinions. There are NO viruses in the wild at this moment for OS X, and there really hasn't been in a while. So I believe that there is NO need for A/V for Macs. There is, however, other malware out there than viruses. There are hijackers for your browser and some malicious ransomeware that has used Java and Flash to lock up Macs. I use Ghostery (either the Mac App Store or ghostery.com) to block everything, including trackers, ads, popups, hijackers and malware, and then if anything gets through, I have malwarebytes (malwarebytes.com) to remove it. I don't download from download.com, cnet.com, softonic.com or any other "aggregator" sites that have software. I stick to Mac App Store and developer websites I trust or which are recommended by people I trust. I don't use torrents, stay away from pirate sites and don't do porn.
If you surf safely and do the ghostery/malwarebytes approach, you should be safe.