I have absolutely no idea why they purchased Nokia in the first place -- it was obvious that they were never going to seriously challenge Apple or Google, and Nokia was another obviously sinking ship. It was like if Circuit City had purchased Radio Shack. I have no idea why the board let Ballmer blow billions on an acquisition they knew he wouldn't be around to see through and that didn't fit with the strategic direction of the company 6 months later.
If I were an institutional investor, I would demand a change in board leadership. This kind of stuff is just unacceptable for a public company. I know hindsight is 20/20, but blowing $14 billion on acquisitions that were doomed to begin with is simply inexcusable. You can blame Ballmer for being a terrible CEO, but the blame really rests on the board for allowing him to make really big, really bad decisions.