Apologists for advertising usually like to spiel about about how ads provide useful information for people, providing it in a pleasurable way, and besides, their ubiquity proves how ineffective they are -- if they really worked there wouldn't need to be so many of them, repeating themselves so often. Obviously this is sophistry -- ads are ubiquitous precisely because they work, and their effectiveness prompts escalating saturation battles between firms fighting for market share. The less intrinsic quality there is to a product (the more it is a commodity distinguished only by brand name), the more critical advertising is to making profits.
Exposure to advertising tends to lead us to try to build up defenses against them -- sometimes these defenses provide a false sense of security, as when ads try to sidle up to us and reassure us that we're realy smart, and oh, aren't ads silly? and by the way, here's something you really need to stay as smart as you are. But generally these defenses allow us to filter out many commercial messages and discount the information provided in those that get through (always the most dangerous ones, because if they have passed the filter, that means they are likely telling us something we really would like to believe). Hence advertisers like to target a group without any defenses: children. Via BoingBoing.net comes this link which details a recent study that shows children's demand for products increases with their exposure to ads and product placements. the researchers conclude, "The current study does document that screen media exposure is a true prospective risk factor for subsequent consumeristic behavior, adding to the evidence supporting behavioral and policy interventions to reduce children's exposure to screen media and advertising, whether implemented at the individual family level, institutional level or the population level through legislation and changes in social norms." In other words, America should legislate children's advertising out of existence, as has been tried in several other countries.
Will this do any good? I wonder whether the exposure to ads builds up the child's anti-ad defense system or whether it creates a kind of apathy toward them. Or does it make children tolerate them when they shouldn't be tolerated (as in movie theaters -- people used to boo the screen when they showed ads, now people hardly notice). When you haven't watched TV in a while, the first thing you notice when you do is how irritating and invasive and shrill and intrusive the ads are, and how the rhythm of the programming is designed to serve them (with precommercial cliffhangers or dramatic tableau). Attempting to protect children from ads may give ads an even more seductive power as something forbidden, making them a signifier of adulthood and thus giving them an even greater power to confer legitimacy, social recognition, the sense that one has arrived -- the very thing most ads use to sell products in general.
If ads were simply givign information, then they could be thwarted by providing factual information from nonprofit or government sources. But ads don't provide information so much as they provide a sense of belonging. The most effective way to undermine the efficacy of ads would be to set up an alternate source of social recognition, to empower social networks independent of corporate sponsorship. Would such a system prove resistant to the likely attempts to commercialize it? Probably not. (Witness MySpace, which takes fledging friend groups and moves them online so that they can be commercilaized.) So the best way to evade the effectiveness of ads is to make marginalization one's personal goal -- be a weird outcast on purpose, in what could be called the Goth strategy. But this is a kind of self-sabotage, as a reputation for being anti-social isn't likely to sustain one's sense of identity or social accomplishment. For better or worse, ads are safely ensconsed at the relay between public and private and are able to insinuate themselves into the circuit of social recognition.