the controlled and disciplined scenario generation method, as well as the formal education required are part of what turns this "witchcraft" into a science, or at least a practice worth considering. it is in fact taught in such places as Cornell, Leeds, and yes, even Bar Ilan :) look under "Future Studies".

regarding the method, i highly recommend a quick googling of future studies. it is vast and deep, so for lack of space i will just mention system dynamics, very formal education, delphi, as well as guided imagination and brianstorming.
about the number of scenarios generated, the GBE group in RDShell generates just three (3!) scenarios a year. that has got to put the Gurbachov scenario in a more impressive light.
Furthermore, RDS has a system in place dubbed TINA (There Is No Alternative) which guides them in their business and policy making process. in a nutshell, element that keep popping up in all scenarios and cannot be eliminated are "in your face" enough that they cannot be ignored when drafting a policy. Mr. Wack himself acknowledged the likely dilution of this method as more and more people start practicing it.