I think this is the key. Samsung are the target because they're making a huge success of their phones and threatening (even in the US) Apple's position as the perceived 'gold standard' for smartphones. That perception has already faded away in other parts of the world.

Perhaps they are only suing Samsung because only Samsung's designs are close enough to be covered by their design patents. That doesn't mean (to me) anything other than that the patent system is broken. I don't think that proceeding with these lawsuits is the right thing to do. Just because you can doesn't mean you should.

I agree MS's android tax is just dirty, btw.