One of their points is that the process may be as valuable as the end product:
There is also value to conducting Global Trends exercises even if the results only minimally improve our knowledge of the future. The process of creating these reports links the intelligence community with smart outsiders -- in academia and business -- who have different perspectives on the world. The reports also force policymakers to step back from the day-to-day and think hard about big-picture trends.I think that's part of the value of some other government studies and reports, including the National Security Strategy Report required of the President. The final document is often fuzzy, but the effort to solicit views and craft it is enormously useful for any administration.
By the way, this report appears on a new section of the already quite excellent Foreign Policy magazine site. FP has added a "National Security Channel" and some blogs, including one on the Pentagon that appears to be as newsworthy as the existing blog on the State Department, The Cable.