I think that product placement on television is an effective way of advertising. Product placement seems, to me, to resemble subconscious advertising, because the viewer is not necessarily directly informed that they are being advertised to until after they see the product, and whether or not it registers for the consumer that they have witnessed a subtle ad, the image probably more than likely sticks in their head. Its not unexpected becuase the media is always trying for the next best way to advertise to consumers, neither is it significantly wrong when compared to some of the other extremes media has utilized to reach consumers. Its just another example of how media can affect and reach people without many of them knowing.
Product placement also seems like another form of a testimonial of sorts. The only major difference is that the clelebrity or medium is not directly endorsing the product, but rather indirectly, which can sometimes have the same effects, it just depends on who's watching and paying attention.
Teenagers, more than any other age demographic, are porobably more likely to be affected by product placement. Teenagers consume more media and products than any other age group and are more aware of the brands out there. Also, teenagers are at an age where being cool and fitting in are emphasized, and when "cool" is associated with celebrities, clothing, or movies, for example, and celebrities and movies are associated with certain products, then deductive reasoning dictates that teenagers are going to be attracted to the certain products.