Marketing, sales and the psychology behind consumer equilibrium -- To what extent are corporate marketing campaigns chief influences behind your ranking of marginal utility?

Have you ever consumed a good that was heavily marketed, thought you had attained consumer equilibrium, only to have understood later that you had overvalued your metrics?

Since the law of demand is derived from the law of diminishing marginal utility, can't the corporation get at the values of diminishing marginal utility and orchestrate them to shift demand in their favor?

Does the psychology behind consumption ever confound economists who try to measure, identify and then predict consumer behavior?

In short, aren't our decision making skills more complex than the mathematical model of this week?