While I generally agree that an idea is not worth the paper used to write it down, there is also a certain level of domain expertise that a coder will lack which an "idea person" can supply if they have the right sort of experience. You may be a rails "rock star", but if you don't know dick about the widget* supply business then your widget management app is not going to go anywhere.
*I do hate how useless wen plugins have appropriated a nice generic term...