Fortune has a lengthy scoop on Sony's decline and Sir Howard Stringer's attempt to recover/revive/reinvent it. Quite long but very insightful.
This paragraph is the best explanation of the Sony's stumble.
The culprit in nearly every case has been Sony's tradition-bound mentality, one that remained too focused on building excellent analog machines in an increasingly digital world
I like this paragraph most, it best reflects the inefficiency inside Sony.
How was it that mega-hit music games Guitar Hero and Rock Band were developed elsewhere, while Sony owns one of the world's largest music companies?