“Personal anecdote trumps data.” F. Joseph Merlino
Unfortunately, that has been the case in terms of measuring the effectiveness of education materials. But today there is What Works, a clearing-house of educational tools ("programs, products, practices and policies") that have been tested using the research methodologies (e.g., double blind clinical trials) usually used in the medical industry.
Interestingly, the non-profit world is also facing a similar dilemma. Are their efforts effective? While they are dealing with a lot of push-back, mainly of the "the transformation of lives can't be measure" kind, it would be interesting to see if they will adopt more rigorous testing. For an interesting story on the challenges faced by non-profits/philanthropy in this regard, see this American Life episode.
Finally, and more important to me, I would like to see soft skill development subjected to the same type of rigor. How can we help people develop skills like self-awareness and how do we measure whether or not our efforts were effective? I believe companies are a great starting ground for this type of exploration and "workforce science" seems to be a good start, though less focused right now on soft skills, as opposed to technical training.