PMO as a panacea?

It seems that everywhere you turn, someone is recommending a Project Management Office as the solution to an organisation's project management woes. This 2003 article from CIO magazine makes a familiar point and provides some statistics that still have validity. Office Discipline: Why You Need a Project Management Office
The reason for bringing up the topic again now is that I recently came across a situation where a client was planning to implement project management tools - and to leave the project managers to use them as they saw fit.
McHardy's conjecture states that 'for business processes, whatever is not deliberately held together will fly apart'. In project management process terms this applies when artifacts - tools, procedures, templates, guidelines, etc. - are made available without any mechanism for coordinating their use. This is the 'discipline' referred to in the article. Without the requirement to apply procedures consistently, individuals will tend to develop their own solutions and approaches that are reasonably tailored to their own circumstances. Sometimes this will be based on tool preferences, local reporting habits, work profiles or requirement to conform to alternative procedures.
PMOs can take various forms but one common requirement is for the PMO to provide the glue to hold the processes and their use together. Even if there is no formal PMO there needs to be some cohesive mechanism to make sure the expensively acquired assets areused.