This is not the case. Macintosh's are not immune to viruses and Mac users can also be victims of phishing scams. This is what Jacob Appelbaum, a hacker and researcher, has to say about the subject.
It's possible to have a well-secured machine regardless of operating system. Users generally aren't able to secure machines and so this responsibility often falls to the vendor...Mac OS X and Windows both encourage users to download programs from the Internet without any thought for security.
Graham Cluley, a senior technology consultant at Sophos, comments similarly on the issue:
I would argue that an Apple Mac user wanting to watch the 'Erin Andrews Peephole Video' is just as likely to download a bogus browser plug-in to help them do that, as a Windows user. And it doesn't matter that Mac OS X will ask them to enter their username and password to install the plug-in--they want to watch the video, they will enter their username and password.
It is also a misconception that Macintosh's are also immune to viruses. Macs aren't immune to viruses, but they are very rare. I do recommend users use antiviruses on these operating systems. The reason that there are less Macintosh viruses is that Apple holds less market share that apple and thus this means that designing a Mac virus would mean that less users can be targeted.
Tony Bradley from PC World made this comment, backing up my point quite nicely:
... the primary reason Macs aren't attacked and compromised more often is that the platform with 92 percent market share promises malware developers a significantly higher return on investment than the platform with five percent market share.
This was quite evident where at a security conference in Vancouver, "smart people" hack into fully patched and secure machines in short periods of time.
The Apple iPhone 3GS was fully compromised in 20 seconds by two hackers, the first time the mighty iPhone 2.0 has fallen to a crack. And the infamous Charlie Miller, who has successfully hacked into fully patched Macs for the last two years, this year wormed his way into fully patched and secure MacBook Pro to take home a cool $10,000. Another guy slammed into a fully-patched Windows 7 machine.
What was my point? Macs can be just as insecure as Windows if hackers out there feel like hacking it. Luckily for Mac users, many hackers aren't.
If you feel that this article is incorrect (factually), then feel free to argue it in the comments.