People don't know what they want; they only know what they know

"People don't know what they want; they only know what they know."

I have heard this saying many times before and I've always agreed with it. There are so many products we  have no clue about but if we did we would want them. The majority of consumers do not have the intillectual ability to forsee changes in industries and new technology in products. This is where marketing experts and engineers come in. It is impossible to know if one wants something if they do not know it exists. It is the job of the marketing team to convince someone that, although they may not even know exactly what the product is, the consumer needs it.

I think a great example of this saying and accompanied marketing strategy is the tablet industry. When Apple first introduced the iPad no one knew all the capabilities of it right away but by the way Apple marketed it's product made consumers drool over the possibilities. It was Apple's research and development team that told Apple executives what the next big thing would be. In turn the marketing team made sure that even if you didn't know exactly what it was, you still wanted it, and would pay substantially to have it.
Do you guys think companies completely influence are wants? Or do we already have an idea before we see an add?