This is a good point not mentioned yet. The number of viruses targeted to an OS is directly proportional to the market share it has. As long as it stays in sing

This is a good point not mentioned yet. The number of viruses targeted to an OS is directly proportional to the market share it has. As long as it stays in single digits any "economically rational" virus maker will write yet another windows virus instead of working on an unfamiliar platform. Whether it will be technically more difficult to write a virus on linux, max of chrome os, we will only know for sure when/if they become a target tempting enough.