And who took care of all these functions previously? Excluding the new technology, which is just technology, all what Forrester describes have been a standard. And even more at the time when IT was a profit center - yes, it was "funny money" inside a company but made the budgeting, management and user / customer interactions much more clear.

Another problem I see in "specialization" is that an infrastructure is a company / corporate wide entity - you just can't manage storage, network, physical, whatever security, capacity, performance, etc at separate components of the infrastructure - who's job it is to design and to see that the whole runs well?