For a very long time Mac users have reassured themselves that the nasty stuff will always happen to those uncreative and unimaginative Windows users. As a consequence an astonishing number of Apple OS X users run their computers with little to no regard to security or anti virus protection.
If you are one of them then it is time to STOP!
The Register has a couple of articles that should make it abundantly clear that Mac users need to get their act together and install anti virus and assume that when travelling the web that they are just as likely to have their identity nicked or machine taken over as anyone else.
Here are the links: