Just read an article by Alistair Cockburn about the Taylor-ism of Software Development. I have to believe he's onto something. It seems that the whole system, starting with the Forrester researchers and reaching into the larger organizations, are reacting to the paradigm shift that Agile represents.
Kanban is an easier system. No org changes. No team bonuses. No silly commitment. No estimation. Its all about the flow.....
Seriously, I've only used Kanban at my current employer for those who cannot achieve true agility. Perhaps they don't have a good product owner. Perhaps they don't have a cross-functional team. Perhaps they're really small, or they can release whenever they want to ( read: facebook) . Then great. Just throw that stuff out there.
For me, I like the cadence and discipline an Agile process will provide teams and organizations. I like it in the middle, where the value can be released iteratively. It is possible that an enterprise could roll iterative products into a kanban to flow the release, but for me, I'll take the iteration over some nebulous flow any day.