Communication and trust between the marketer and customer the most important factor in marketing. Because marketing is designing and setting goals for the future, it is not something where you can simply sign a contract, with the respective parties, executing the terms.
It is important to note that it is a partnership. If you work together with good communication toward the same goal for the future, you will be able to reap the rewards later. Without proper communication, you will be unable to set proper goals and you will waste money and energy on improper targeting.