I think he wasn't responsible in the sense that he was simply present for a naturally emergent phenomenon; but at the same time, he was responsible for actively participating in and promoting that phenomenon.
Responsibility is relative to authority, and Spolsky ended up with a very significant amount of authority. Whether or not his behavior was good or bad, it's pretty clear that he had more responsibility than any one person really should. I wouldn't consider that his fault: he didn't really seek it out, or intentionally abuse it. I would, however, consider it what happened.
If we tack a step back, and look at this scenario as a system, we can see that it's the structure of the system itself that lead to these problems, not the intentions of any of its participants.
Now that we have the power of hindsight and objectivity, we can use that to design a better system. The big question is, will we ever get around to implementing it?