I think advertising, as it's done in America today, is inherently unethical.
People set up focus groups to figure out what colors and sounds and images will trigger thoughts and feelings. Casinos are red and flashy and loud to get you to spend more and move faster. Restaurants will have bright lights and peppy music so you eat faster and clear the table for another customer. SUV designers play to concepts of dominance and power. We still have free will, but a soda commercial makes you thirsty and a billboard with a burger on it makes you hungry. All of this is not to remind you that the product still exists, but to urge you to purchase that product, to remember that brand name. In that way it, even in a small way, reduces your input on the decision.
After I stopped watching TV I realized I didn't crave junk food anymore. I was already fairly spartan in my tastes but I realized that I wasn't thinking about wanting new possessions anymore. If I'm on the computer and ads are in the sidebar and I see some pizza ads, I'm noticeably less likely to want to cook dinner, and instead get lazy and decide to order something.
Secondly, advertisers lie. By not giving you the full information you don't have as strong of an ability to make a clear decision. When is the last time you ate at a restaurant where the food actually looked like the ad? Restaurants that nice don't advertise on TV. The Big Mac or pizza you see is a room-temperature piece of art, blowtorched to perfect brownness, screwed to a plank and raised up with cardboard inserts. That assumes it hasn't simply been CGd to death after filming. Your truck will not do what the truck on the commercial does, and your hybrid will not get that mileage unless you drive like a grandma. That video game commercial is showing cutscenes, occasionally in-game footage, but it's shallow and lame compared to how they describe it. Quotes from people and publications are generally purchased or come from people who don't matter.
Thirdly, because advertisers are so insistent and obnoxious, we tune them out. We TIVO past the commercials or use Adblock online. We have spam filters on our email inboxes and even set up fake email addresses to use when signing up for a thing so that the info doesn't get sold. The reaction they should have is, "Oh, people fucking hate ads, maybe we should figure out some other revenue scheme" but instead they just get more obnoxious. They fill our mailboxes with junk mail, they call and text. In my hometown they made it illegal to add new billboards, but the existing billboards are grandfathered in. People argued that outlawing billboards entirely would detract from revenue that the landowner had before. I can see why they would not want to make less money, but I can come up with a dozen counterexamples which show their argument is bullshit. But they got their way!
The Internet is packed with shitty ads that can even be an attack vector, depending, and yet we're OK with it. Because we ignore them. But they fight back. Advertising interests want to make money off the Internet, and are slowly screwing us all over doing it. Youtube used to be profitable without video ads. This flash game site I play on called Kongregate has started playing video ads before loading a game. You watch a TV network's website like ABC and the videos, which barely work anyway and are never the most recent shows, are still packed with sometimes a half dozen ads per commercial break, and 3-4 breaks per episode. Yet their costs in delivering that show are lower than when broadcasting. I believe advertisers, individually self-interested, would be willing to effectively destroy our enjoyment of the Internet (a thing much more important than they will ever be) just to keep making a buck. And when they're done, they'll move on to the next beautiful thing to destroy it.
I don't wear clothes that have logos. If I really want that clothing and I can remove the logo, I do. Frequently a jacket, for example, will have the logo as a separate piece of cloth or rubber and you can snip the stitching and pull it off without damaging the jacket. Shoes are more difficult. I feel that if I'm going to walk around showing the logo, I'm advertising for their company. I should get the product cheaper if I have to show off a logo, or else get a monthly check. If I put a wrap on my car to advertise some payday loan shark or accountant, I get paid. I don't see why it shouldn't be the same for clothing.
But there are companies that do not advertise, yet remain successful. There are cities that have outlawed billboards. There are websites completely without ads that still turn a profit. If tomorrow every ad man and woman woke up and decided to spend the rest of their days surfing and eating milkshakes and carving ducks out of driftwood instead of making ads the world would be a far better place.