Bill Starbuck (his homepage) is a professor of creative management at Stern, whatever it means. According to him, the strategic planning is a failure at best, or a hoax. The reasons are (the following is a summary of pages 42 — 48 of A perfect mess which presumably is a summary of his essay, Strategizing in the real world):

• It works only according to researches that are biased toward them;
• Managers know nothing of important;
• Organizational structure reinforces ignorance, distortion of perception and “massaging” data to make things appear better;
• Managers can’t read the future. “One study found that a technique of simply guessing that the gross national product will remain whatever it is right now for the next three months did better on average than three out of four of the government’s leading models. A technique of guessing that the GNP will change over the next three months exactly as much as it changed over the past three months did better than all four. Businesses, of course, rely heavily on the government’s models for their own strategic planning” (pp. 45 — 46);
• Even if based on solid data, the planning is a waste of time, because for planners it takes months or years to build the model, but for competitors it takes a lot less. In other words, there’s no spoon first-mover advantage;
• Long-term planning blocks your efforts at improvisation, which is essential at a rapidly changing environment;
• It’s not that good planners do better. Rather, it’s the reverse: Better performers have extra money, time and confidence to do the planning. Afterwards, they do poorly, mostly because of the planning; and
• Despite the facts, planning thrives because of people engaged in the business — management consulting.

It’s an interesting argument.