Everybody who doesn’t already know the proper answer. C’mon, we are supposed to be fighting ignorance, after all. 
It just seems to me that advertising is one of the most complained about and least understood topics in the world. (Along with taxes, religion, capitalism, sex… make up your own list.)
And exposure is just one of many aspects of what makes advertising work. It’s necessary, but not sufficient. Advertising has to be memorable, has to promote the brand, has to reach the target audience, has to put the product in context, has to differentiate the product from its competitors, has to do a million things in a very tight space.
Trying to study the effects of advertising has baffled more people for more years than anything else (except for taxes, religion, capitalism, sex…). How do you measure the results? How do you isolate the particular ad? How do you account for long-term persuasion? How do you subtract other cultural traits?
Advertisers do everything they can think of, and lots of Ph.D.'s have put lots of hours into thinking up stuff they can get paid for, I mean, scientific studies. But no one has ever solved the problem. Too many variables. Too hard to come up with control groups. Too many types of ads and media. Too short times before new campaigns come along.
If scientific studies worked, then they’d be used and ads would work. Right now nobody knows. It’s like self-help books. If they did anything more than make people feel good for having read a self-help book, they’d stop selling. Or all but one would stop selling.
About all that anyone can say is that any one company that stops advertising suffers a loss in market share compared to the companies that continue advertising. Most of the time. In most industries. Except for cash cow products, old favorites with a set market share and audience that don’t need any more push. So in that sense, advertising does objectively work. Or maybe marketing the brand does. Or something. But what works, and which ads work and which don’t, and why those ads work, and what media to put those ads in, and how many of them to buy, and when too much exposure is no good, and fifty other questions continue to cause execs to get ulcers and go bald and those other Madison Avenue clichés. Nobody knows anything except that they have to keep on doing something or die.
What a way to make a living.
Sorry, I just feel like lecturing today.