Someone reminded me yesterday of a talk David Lewis and I gave at one of the Information Design Conferences in the early 90s. We likened the information design process to a lens. Information designers take requirements and constraints that were previously uncoordinated and unrelated, from different parts of an organisation, and focus them in a single design solution that is coherent and usable by customers.
Then, as we consult and amend our perfectly-focused solution, it shifts just slightly out of focus before it's implemented. The final solution is never as good as the penultimate one.
And finally, there's often a stray photon that arrives from nowhere, completely bypassing our lens. The marketing director's twelve-year old son has drawn a great logo (it's happened); someone has read that italic is always illegible; someone doesn't like green.