One school apparently believes that marketing agencies are basically an extension of the company’s marketing department and should simply execute assignments. Marketing directors who subscribe to this school are generally of the opinion that he and his team could do what the agency does if only he had the time or resources. This is the "buy the dog and bark myself" school. A variation of this is the "guess what number I'm thinking of" school -- where the marketing director has an idea in mind about what she wants and makes the agency keep working until they guess it.
Another school propagates the belief that the company's customers know what they want and will tell us if only we ask them and thereby relieve the marketing director of responsibility for the effectiveness of the communications. This type of marketing director “plays it safe” by having everything the agency creates vetted before research groups. The result of the research is used to direct the course of marketing campaigns. This is the "let's test it" school. A variation of this is the "we asked around" school -- where ideas and campaigns live and die based on the marketing director showing them to colleagues, friends and family.
Finally, there is the school that encourages marketing directors to work shoulder-to-shoulder with the agency to encourage them and make certain that they know everything about the product and the market the company serves. Research may be used to uncover consumer insights but not to test communications (which can never really be tested in a vacuum). This marketing director then works closely with the agency team to develop a document that clearly establishes the goals and reasonable criteria for the program…then let's the agency loose to develop ideas and strategies. These ideas are then executed with only modest revision if necessary. The marketing director guides but does not dictate. This is the "hire great people and let them do great things" or the "ready, fire, aim" school where great ideas are allowed to succeed or fail and then try again. Yes it's brave. But it's the only way to really get it right.
Which one are you?
I have sat on both sides of the fence, as agency head and on the client side as marketing head. And I have always held the opinion that agencies make recommendations and clients make decisions. It’s the client’s money after all. However, the advantage of hiring a great agency (granted, they are not all great) is that it can use its unique perspective to balance and marry the needs of the market and the marketer. But if it is made to be a slave to one or the other, it can't ever be creative or effective in a way that every marketing director demands, yet few truly encourage.