Makers and thinkers

Paul Isakson, the Director of Brand Planning of Minneapolis digital agency space150, used the Venn diagram above to illustrate the possible value an ad agency could add. In his blog post The Core Competencies of an Agency, he concludes: "I think the days of getting by on great service are done. If I were a client, I'd nix the retainers and pay for ideas and execution of those ideas. I'd hire people and agencies great at thinking and get them to give me their best ideas. Then, I'd find the best makers and get them to bring them to life. I wouldn't want to pay an agency to suck up to me with a bloated staff. Just bring me great ideas and if you can't make them, help me find someone who can."

I'm not sure if I agree. This strategy depends a lot on the skills and knowhow of the client. Maybe he's easily impressed by the "wow" ideas, but cannot assess if, e.g. it is technically feasible and scalable. Or picks a subcontractor who is unable to interpret the "wow" idea into a working web concept.
What do you think?