I have learned to respect ideas, wherever they come from. Often they come from clients. Account executives often have big creative ideas, regardless of what some writers think.
A good basic selling idea, involvement and relevancy, of course, are as important as ever, but in the advertising din of today, unless you make yourself noticed and believed, you ain't got nothin'.
To swear off making mistakes is very easy. All you have to do is to swear off having ideas.