"Yet...these critical infrastructure elements are usually procured, managed and run separately, resulting in a fragmented infrastructure..."
In many companies there is no integrated thinking in first place, even after we implemented ITIL. Andrew Buss is talking about changing silos to a layered service delivery. Sure enough, there are challenges here, e.g. the compartmentalization due to PCI-DSS req 6. But Andrew is coming bottom up from an infrastructure viewpoint, many companies however start top down. For example, "we need to provide this trading functionality using that application because the sales rep bought us a steak lunch. And, uh, let's throw some money at some tin. Er, we need, servers, storage and networks." All items that I mentioned here are products, or solutions to requirements. Even Andrew still makes the distinction between these segments. Unfortunately this is 1980s thinking and simply wrong, and also is not remedied by deploying management software like Oracle Enterprise Manager or a bunch of tools from BMC or VMWare.
The infrastructure today is still defined by the sales reps that are selling us the servers, the routers and the storage. The first step to a more flexible IT model is to liberate ourselves from them. This means "mail service" instead of "MS Exchange" and "data, backup and archiving service" instead of "SAN".
After that, we talk about continued business justification, roles and responsibilites, tailor to suit the service/the customer, etc.
And, boy, do you get results once you get external parties out of the equation!