Not a stat I would defend. There clearly is a market as there are numerous offerings from companies, including some that are Mac only. If you share files with a PC, it's nice of you have to do an occasional scan. Secondly, a lot of universities and businesses will require all users (including those running OSX) to have virus protection on their computers to be part of the network, both of my last two employers will have it.
Well I agree with you that there aren't any now, that doesn't answer the OP's question. Although searching would have produced something.
