I just recorded a podcast with Gerald Leonard over at Principles of Execution and part of the discussion was about how the PMO is really just the custodian of a Portfolio. The only reason a project portfolio exists is to deliver on business goals, and so the portfolio really belongs to "the business". But in most organizations we work with, there is little consensus between executives on what the goals are and how they should be prioritized.

 The process of getting agreement between executives on business priorities is, therefore, like herding cats... only these cats are killers because 72% of PMOs are called into question by these same execs.