Power
One day, a talking Chihuahua said to millions of Americans, "Yo quiero Taco Bell," and suddenly millions of Americans quisieron Taco Bell. That's some serious Jedi mind control at work.
In essence, television commercial directors inspire people to buy things they never before thought they needed. Which is a nice way of saying they basically plot world domination on a daily basis, using ridiculously catchy jingles instead of nuclear warheads as their weapons of choice. If you're good at what you do, you're pretty powerful.