Great article, I definitely agree relationships are the oil that keeps the cogs turning.
Just to respond to the resourcing at an agency:
Agency does not equal unlimited resource. There are constraints to the number of projects we can run, best size of teams and number of people available. Every week I have to negotiate internally and with clients to ensure we are working on the most appropriate work streams.
Internally – not just is there available capacity in other teams, but is it appropriate / feasible for the work to be shared (often it’s better to wait).
Clients – we can’t start work at the drop of a hat and all our clients understand there is a minimum lead time between briefing and execution.
All of which puts relationships at the centre of everything.