Well, to be blunt, if you are going to get Picasso to design your logo you _don't_ art direct him. And you try your best not to piss him off. Because he's fucking Picasso...

You don't have to use what he makes, but if you want genius, and why else would you want Jobs and his team to design an ad, you ask politely and then get out of the way.

Edit: Somewhere online I read an article about Jobs getting Paul Rand (edited from Milton Glaser) to design the logo for NEXT. Can't find with a quick Google search, but it was a fascinating read.