I had written this a while ago, but i think it is worth revisiting. Many of the core reasons for the replacement of "Rule of Thumb" practice with "Scientific Management" in the early 1900's have now changed, ushering in an era where we need both. In case you're wondering, scientific management is still the basis for much of today's management practice and organizational structures.
While i don't really agree with Lynda's assertion that the job of middle manager will "disappear," i do agree that the nature of the job is already changing, because some of the original reasons for the necessity of professional managers has changed. I've written about this here: http://www.socialens.com/2009/11/12/recalibratingrule-of-thumb-vs-scientific-management/