I wonder how they count it? Because I definitely signed up, imported my feeds, and gave it a try. But I've stopped using it because it requires a browser extension/plugin which I find irritating. Am I counted in the 3 million?
Similar here, but I haven't used Google Reader for more then 2 years. After all the buzz I thought I'd give rss readers another try. (It didn't last long.)
Same here.
Most probably for tracking. I do not really see any other reason.