I love how the news sites post this as if it were some brand new threat. Botnets have been around for quite some time, and are simply growing and growing due to computer owners who don't know what they're doing. Owners of the botnets make some really nice coin off their dastardly uses.
As much as I agree with you if Microsoft bundled software that would undermind the offerings by many other companies they would get slapped with an anti-trust suit so fast it would make their head spin.
No product is 100% secure even the almighty Linux, they find new vulnerabilities for Linux everyday but MS gets the spotlight because they are big business. Same with MAC, it is not impervious either, there have been exploits for it as well. Users need to learn to be responsible for their actions. Install your updates, keep your anti-virus up to date, and removed unused/unneeded features. It doesn't take much to protect yourself. Would you blame ford if you left your doors unlocked and you car got stolen?