An article at Businessweek.com illustrates the dangers of improperly managing a project.  It discusses the challenges Boeing, the defense contractor, and the Federal government had in managing the the Virtual Fence project and its impact on the effectiveness of the proposed solution.  The Virtual Fence was commissioned by the Department of Homeland Security as a test to see if it could be used instead of a physical fence to secure our southern border.  As Business Week puts it:

...critics contend the government didn't get what it paid for with Project 28 (Note: The prototype fence cost the government $20 million). The Government Accountability Office has said the project suffered from insufficient government monitoring and direction. While acquainted with operating war-fighting systems, Boeing knew little about border patrol realities. "The poorly structured contract that prevented the line Border Patrol agents from pointing out obvious flaws and caused an overreliance on contractors has resulted in a system that has been described as providing 'marginal' functionality at best," says Representative Bennie Thompson (D-Miss.), who chairs the House Committee on Homeland Security.

What happened between Boeing and the government is not uncommon in consulting relationships.  Note that the article states that Boeing knew little about border patrol realities and that the agents on the front line were effectively excluded from providing feedback.  While most consulting companies provide competent advice and often specialize in a particular industry or subject, it's also fair to say that they are not experts in your business.    Only you can be the expert.  Consultants bring value by bringing an objective perspective and, often, empirical data.  Ultimately, the goals of a project can only be met and the expected return realized when the consultants and your organization work together to understand the issues on the front line and to craft a solution that addresses those issues.  By doing so, you can dramatically reduce the risk of a consulting engagement and optimize the return on your investment.