Actually, the best way to fight piracy is to make a product pirates aren't interested in.
Yes, but if you can't communicate your results, what good are they to the rest of us?
I voted for communication because the state of science journalism compelled me to.
While market share might be a factor (infact almost definitely IS a factor) in the security of Windows vs OS X/Linux, IE vs Firefox, etc, it's more likely the architecture.
The architecture of Unix systems (running as root, user permissions, etc) makes/made it very hard for malware to be written for it. At least, to cause any significant damage.
Though in the case of Firefox vs IE, I'm not so sure. I know little about either browser's architecture. But it might not be just market share that's the reason for the huge number of sploits for IE as opposed to firefox.