Peter Schwartz is President of the Global Business Network, a consulting firm that does scenario planning. I'll just give a few sentances of background for the Operations Research people who read this group. In math programming you might develop math models that optimize a portfolio over tens of thousands of possible interest rate scenarios. Current research is on solving ever larger numbers of scenarios. Schwartz's work is for trying to predict large scale trends five, ten, or twenty years in the future.
Strategic planners use it to essentially try to cover their bases.
The Joint Chiefs of Staff commissioned a study by the GBN on the future challenges to the millitary over the next 30 years, as an example. They are more works of fiction than math. Good scenarios can be kept in mind by strategic planners, who try to avoid making decisions that would have catestropic outcomes in any scenario.