by the people that install, update, and discontinue use as well.
Like I said, it does not need to be 100%, and it would be about as accurate as MS's numbers. But it would be a good way to monitor usage overall as most users connected to the Internet will install critical updates.

This can be used without sending data back to anyone, without running a program to call home, and for people who do not register. Honestly, I see no downfall to this except accuracy, but there is no real way to be totally accurate that will appease everyone.