Marketing is real. And it works (obviously).
Yes, but it is not responsible for any actions people take. It cannot force anyone to have a want or to take an action to buy something (unlike what the president wishes to do). It does not take away personal responsibility, nor does it remove the part of your brain that tells you what you should do. In fact, it does not even effectively trick people into thinking a bad product is good. It can trick them into getting a bad product once, but no one would by a second iPhone it were crap.
No, the bigger issue is that we have become effective at making products that do things that we love. The iPhone isn't popular because it has good advertising. Actually, those silhouette ads were horrible. But it brought something that gave us a useful object. It takes a phone, which ~85% of the US population has in one form or another (counting home phones here), and then adds your music library to it (no more CD books in the car), then gives you Internet activity on the road (no laptop necessary), plenty of pick up and play games (don't have to read a two month old issue of Highlights in the waiting room ever again), dozens of books in your pocket, PDA functionality (run your business from your pocket), dozens of functionality apps so you immediately know things like weather and traffic, and access to all the forms of digital entertainment that will make terrestrial/broadcast media irrelevant in a generation (My car radio never leaves auxiliary mode, the Adam Carolla podcast is my drive-time listening, Pandora is my radio, and I listen to audiobooks now that I get the whole thing at the push of a button).
That is why the iPhone is so popular. No single marketing campaign can make people buy an iPhone more than the iPhone itself does. Now, is Apple supposed to not make a device that people will want? Sure, now its functionality is redundant forms of things we have now, but in a generation or two there will be people with 100% digital multimedia libraries and they will be fitting it all in their pocket, and the only hardware will be something like the iPhone.
If marketing were all that was necessary to make people buy things there would be no vehicle test drives or home sale open houses, sites like Rotten Tomatoes would have no readers, and even bad movies would have a good opening weekend. Marketing will make you look into a product, but the product is what makes you buy it.
And side note: Since the 1920s the Magic Bullet Theory has been disproved, reworked, disproved, and currently being used to say violent video games make violent children and, despite what fundamentalists think, has already been disproved.