Like a midwife, I make my living bringing new babies into the world, except that mine are new advertising campaigns.
I never assign a product to a writer unless I know that he is personally interested in it. Every time I have written a bad campaign, it has been because the product did not interest me.
A lot of today's campaigns are based on optimum positioning but are totally ineffective - because they are dull, or badly constructed, or ineptly written. If nobody reads your advertisement or looks at your commercial, it doesn't do you much good to have the right positioning.