What are the methods for implanting hidden messages in TV commercials?
The method that was used to advertise coca cola (as Ben mentioned in his answer) is called subliminal advertising, and some people claim that it is still being used. You can read a bit more about it (if you have the patience) at this link
The method of displaying a product in a film or TV show is called product placement, and it is very common. In many cases, the producers of the film approach a company to sponsor their film, in return for showing the characters in the film using the product.
actually, the hidden messages are in the shows/movies themselves, rather than in the commercials.
One method I know of is inserting a single frame of the product. Coca Cola used it a while ago in theathers.
During the playback of the movie they pasted a single frame of a bottle of coke - you are exposed to it for only 1/24 of a second. this enters your sub-conscience, and sales of coke bottles skyrocketed.
this method is illegal nowadays.
today people just advertise the product. in the movie "Ace Ventora - pet detective 2", Ace drives through Africa and sees a big "Subway" sign.
These have become illegal over the past few years, and are banned in most countries.
I watched a tv commercial not long ago. Its about American Family Insurance or something and the commercial has a hidden message. It represents a Racist theme. I don't want to offend anyone but the method is very obvious. The starting of the commercial shows a hand of a black woman (maid) serving a cup of coffee to a white person. And at the end of the commercial shows the family and in the background is a Hispanic gardener smiling in the camera. Is that what you mean for hidden messages in tv commercials?
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them