Project@Work on The Fox and the Hen House by Dr. Malcolm Slovin:
"On contracted initiatives, the outside consultant project manages the implementation, but organizations must still appoint their own "inside" project manager to track the actual work, or the focus on cost is bound to get blurry.
There are a host of reasons why projects fail. While there are many causes — cost overruns, failure to properly plan for change, inability to meet timeless — a common root problem often lies underneath: The projects are controlled and implemented by the same contractor. In any process where one party is responsible for both execution and evaluation, you’ve got a prescription for trouble. It’s easy to predict the results when the fox is guarding the hen house."