Thought I'd put in my 2 cents here.
While I agree with a lot of people here on why Microsoft should NOT buy out Blackberry, there is only one reason to think of why they may want to consider it. That is, to own the patents. They don't need or want to have Blackberry phones, however, the patents Blackberry owns may be valuable and helpful to Microsoft. If they did this, that is, bought them for the sole purpose of patents, then Blackberry would be pretty much instantly killed off. I really can't see that happening, as it just isn't Microsoft's MO lately of trying to help and assist other companies as opposed to killing them and taking their stuff. Sure, they bought Nokia's phone division with all the patents, but didn't kill it off. They bought it to save it and to make use of it. If Microsoft wouldn't be able to make use of it in a big way, then there is no reason to buy Blackberry.
However, Blackberry may be doomed in the coming years anyway with Microsoft's Windows 10 possibly taking over the Enterprise sector. That would be cool. Not cool for Blackberry being doomed, but cool if MS takes over the enterprise mobile sector.