Facebook for Android has close to 1 Million users, does that mean Android has sold 1 Million handsets (It has 300,000 activations everyday). I think assuming that everyone in this world is on Facebook is a wrong assumption.

But Microsoft made an active decision to integrate WP7 with Facebook. Beyond that their marketing for the phone revolves entirely around social {or more accurately keeping up with your social network without spending your whole life doing so)

CNN even had an article entitled "WP7 is the real Facebook Phone" (http://articles.cnn.com/2010-10-15/tech/windows.phone.facebo...)

Put another way WP7 is to Facebook as Google Services are to Android. There might be a few rare individuals who use Android but don't have a gmail account but those people are by far the exception.

Do the numbers you're quoting include the people using Facebook through that built-in integration (the People hub)? Or do they only count the dedicated Facebook app?

It's more like 25 millions: http://statistics.allfacebook.com/applications/single/facebo...

No, the numbers dont mean anything in an absolute sense, but I can see the validity of an apples to apples comparison of the Windows 7 FB numbers to Android FB numbers. Although windows must have a greater % of users using FB

Are the users just using Facebook through the People hub counted here? I suspect many or most don't bother installing the dedicated app.