When you're running Windows on a Mac, you're as vulnerable as any Windows user. An interesting question is, would a malicious Windows program affect Mac files on the same computer? It's theoretically possible but extremely difficult to pull off and would reach a very small audience in the Mac market.

Unless they consider themselves very savvy, Mac users should run anti-virus software just like Windows users. Mac users need to start developing a sense of cynicism about content that comes unsolicited, even if it appears to come from a user they know.

Even corporate IT people didn't do it. Some of it was due to laziness and some of it was due to the fact that people don't think about this.