In Defense Acquisition 101 the first lesson might be that it's all a giant mess. But if you really want to know how the system works and doesn't work, Secrecy News has uncovered a brand new report on the whole system put out June 4 by the Congressional Research Service.
CRS sums up the problems.
The complexity of this system of systems combined with the magnitude of personnel, activities and funding involved in its operation can result in problems, including inefficient operations, fraud/waste/abuse, and inadequate implementation or enforcement of the myriad laws and regulations that govern it.
--Catherine MacRae Hockmuth