Just as your funny bumper sticker might offend the guy behind you, your ad may not be saying what you want the target audience to hear
Recently a colleague told me an anecdote from her personal life. She went out with a guy who had one of those bumper stickers on which an ersatz Calvin (from the comic strip Calvin and Hobbes) was relieving himself on a Florida State University logo. When he called her for a second date, she declined. It wasn't that she had an affinity for Florida State, it was just that (in her words), "I thought, clearly I can't have anything in common with someone who voluntarily drove himself to the store, purchased that sticker, and applied it to the back of his vehicle."
That's one of the problems with bumper stickers. The young man who put Calvin on his truck no doubt thought it was funny, preoccupied as he was with putting down a football rival. But the message it conveyed said more about him than he thought, and it cost him that second date.
When you put a bumper sticker on your car it represents just one element of your personality; it's one small sample of how you look at the world. Yet to the guy stuck behind you in traffic, it's the defining element of who you are. As a result, the message you send can become louder than intended, and often misunderstood.
The Message Is Everything
Take, for example, the "my child is an honor student" bumper stickers. That's a nice thought. And Mom probably put it on her minivan out of a combination of delight with and obligation to her wide-eyed sixth grader who proudly brought it home. She displays it to reward her child for his hard work, not to brag. But not every other driver interprets it that way—that's why we see stickers that say things like "my kid can beat up your honor student" or even "my French Bulldog is smarter than your child". (Yes, that's a real sighting.)
The same is true of advertising. It may be O.K. for you to risk the ire of other drivers by virtue of the stickers you put on your car. But when you're paying big money to run an advertising campaign, the message your audience receives is everything—regardless of what it is you intend to say.
A marriage counselor friend of mine defines communication as "the meeting of meaning." I think that's as good a definition as I've heard. We don't truly communicate simply by speaking to someone, we communicate only if they understand what we mean for them to know. The trick of creating effective advertising is to get inside the skins of your target customers, to see your message through their eyes and hear it through their ears.
How You Say What You Say
When you do, you might be surprised at how they interpret what you're trying to say. Here's an all-too-common example. When you hear retailers yelling (as they so often do), "There's never been a better time to buy," you don't think, "There's never been a better time to buy." You think, "There they go again, trying to coerce me into buying a car/sofa/TV." Not the message they intend, but by failing to take into consideration the fact that you may have heard that line once or twice before, advertisers can be their own worst enemy.
Or consider the positive example of companies such as Nike (NKE), Apple (AAPL), and Gatorade (PEP), which rarely overtly ask people to buy anything. They simply develop appealing, interesting, often thought-provoking advertising that involves consumers in the message and invites them to draw their own conclusions. Even more direct-response-oriented brands such as Geico, eBay (EBAY), and Capital One (COF) know how you say something is as important as what you say. Because they've done such a good job of understanding who it is they're trying to reach, their ads have a positive effect.
You aren't the target
Remember, it doesn't matter what an advertiser intends to communicate, what matters is how the target audience interprets the message. Don't just put an ad out there because it sounds good to you. You may like what your advertising has to say, but that can be misleading. You, after all, aren't the target. In fact, since you know so much about your products, your industry, your competition, and even your own good intentions, your reaction may be as far from the target's as it can get.
Learn the lesson of the bumper sticker. Study the people you're trying to reach. Get to know them. Understand their attitudes and perceptions, even if you think they're incorrect. And don't just say what you want to say. Make sure you achieve the meeting of meaning, and save self-expression for the back of your car.