Apparently Apple started encouraging users to install Antivirus on Mac OS. Informed people did never believe on the virus-proof Mac OS theory, Mac users (me included, just using ClamAV on demand!) could afford not to use those just until the critical mass was reached. And it seem to have been reached now.
Is this a bad indicator to Mac OS? Hell, no! It's a natural consequence of Apple's growing market share. Good for them. Congratulations!
PS: if this info is confirmed Windows will receive an apology letter from Mr. Jobs, right?