This Meta Group article gives the result of a survey that reports 73% of IT organisations did not expect their projects would be within 10% the budget. 14% had no expectations at all! Does this matter? When projects are the mechanism by which organisations implement change, it certainly does. If you can't predict what it will take to implement change, how do you know how much change you are capable of implementing, when and how can you integrate various changes from multiple projects.
The conclusion is that organisations must have effective governance processes. The article goes on to describe some guidelines for what constitute good governance methods.
Project Management Essentials: IT's About Governance