When you get a car, there are certain assumptions that are definite. It's going to have an engine. It's going to have windshield wipers. However, the difference between these two things is that windshield wipers came much later, AFTER other people made businesses in enabling people to "see while it's raining". At some point, a secondary technology becomes so invaluable that you can't imagine the first existing without including it. Find me an OS, any OS today, that doesn't include a browser of some kind (whether it be free, Free, or monopoly).
Somewhere along the line McAffe and, to a lesser extent, Symantec, should have realized you can't have your business rely solely on fundamental flaws in other products. You're relying on their business model, then, and if they fix it you're sunk.
If MS closes the gaps better, they're screwed. If they include their own antivirus program, they're screwed. No matter what way you slice it, MS is actually doing the "right thing". Those doing "the wrong thing" decided their fate years ago.