Aren't you being a little naive not to think about the possibility that this was only done by B&N to push a better offer from Microsoft?

Yes, because MS Office, Visual Studio, games like Flight Simulator, Halo, Age of Empires etc are miserable failures. And that's just off the top of my head. Hell, even Microsoft's mouses and keyboards have always been held to high standard.

It is based on Linux, anyway - https://linux.slashdot.org/story/11/10/01/172205/nokia-preps-linux-os-for-low-end-smartphones

Microsoft's strategy has always been thinking long term. Even the first Xbox - that first caused large loss - showed this, as they are now the market leader. This same goes for Bing, Nokia, Facebook, their mobile offerings and everything else they produce.

As for Nook e-reader and Android, I can't be but impressive how cleverly Microsoft has played it all. Essentially they have left all the development costs, problems etc. to Google, while themselves making already over 1 billion dollars a year from Android device sales, and with this recent Nook e-reader investment, they will have a large share in a company that produces one of the most popular Android tablet devices.

Microsoft also starts to control mobile market. They have their own OS, Windows Phone 7, that Nokia - the largest phone manufacturer on planet - will be exclusively using in their smart phones. On top of that Nokia will use Android on their lower end phones, which from Microsoft also collects a large share from.

Microsoft also owns large share of the most popular social network on the planet, Facebook. The one that Google is desperately trying to win (and miserably failing) with their own Google+ service. And the second largest cloud provider after Amazon is Microsoft's Azure, which is used by Apple.

I have to admit, Microsoft and Ballmer have been very clever. Very, very clever.