– Websites that pose as legitimate-looking software vendor's sites, but whose downloads are really Mac malicious code.
– Malware disguised as pirated software available for download from P2P file-sharing networks.
– Sexy online video links that urge you to install a plug-in to view the content, but really infect your computer with a Mac Trojan horse.
– Popular Twitter accounts, such as that belonging to former Apple evangelist Guy Kawasaki, who have tweeted out links to websites designed to infect Mac computers.
It doesn't prove it is common, but it does prove it is out there.