Without strong program management, BI initiatives can spin out of control very quickly due to the ever changing business needs and time required to implement solutions.
Why do you need a Program Manager? Most projects already have a Project Manager and a solid team that will deliver the project, but without a program manager overseeing the overall BI strategy the likelihood of delivering the defined business value is at risk.
Again, Why? The answer is BI is complex - given all the moving parts between the technical teams, software provider(s), users, senior leadership and program sponsor. Just interacting between these different constituents can at times be a full time job and requires specialized skills to ensure seamless communication between all stakeholders and that issues are raised, understood and resolved quickly in order to keep your BI strategy on track.