Marketing aims to shape the cultural meaning of a brand. If someone wants to associate themselves with a particular lifestyle, buying an appropriately advertised label may be an easy way for them to send the desired signal. Advertised consumer goods thus serve people who want to brand themselves, perhaps to affirm their cultural identity or to gain status. Does this make advertising worthwhile after all? (I've always thought that marketers were scum... should I revise my opinion?)
This ties in with important debates over intellectual property and "trademark dilution". See Boing Boing:
It used to be that trademarks were intended to protect "consumers" (that's us) from being tricked into buying goods under false pretenses. If it said "Coca-Cola" on the can, there had better be Coke inside, and not Pepsi or Crazy-Bob's-Discount-House-of-Soda brand. When a competitor of Coke's shipped a bottle of stuff that was misleadingly packaged or labelled, Coke's authority to sue its competition derived from its need to protect us, not its bottom line. It didn't get to sue because it owned Coca-Cola, but because it was acting as a proxy for its customers, who were being decieved by con-artists who mislabelled their goods...
But as time went by, trademarks stopped being about us and started being the embodiment of brands (which, as Surowiecki points out, are on the wane and were probably never as important as we thought to begin with).
This meant that trademarks weren't just things that helped the public know what they were buying -- they are a kind of pseudo-property. Pseudo-property that could be defended on the basis that it "belongs" to a company, who need to be protected from having the value of their marks "diluted" or "tarnished."
So now you have Visa going after eVisa.com -- a company that helps you get travel visas -- and Air Canada going after shareholders who used the Air Canada logo on communications about problems with Air Canada management. Disney's one of the worst, of course, going after daycares that paint Mickey on the walls -- even though there's not an instant's danger that anyone will mistake a nonprofit daycare center for a Disney operation and be misled into patronizing it. Most recently, of course, some of Nintendo's lawyers got a wild hair up their ass because someone mentioned some game titles on a profile-page on a porn/community site and freaked out because the association might damage their brand.
All these new and exciting uses of trademarks -- shutting up critics, blocking new entrants into the market, and controlling the speech of private individuals -- are justified by the importance of brands.
If branding is just a way for companies to manipulate consumers and rip us off, then such heavy-handed legal "protection" is simply evil. But if brands create real (cultural) value for consumers, then there's some trade-off here, and so a real debate to be had.
Actually, even granting this value, I think the pro-marketing argument fails. It shows the value of imbued significance or cultural meaning -- but there's no reason to think that this meaning is best shaped by advertisers. A far more attractive alternative would be for such meanings to emerge from the distributed contributions of cultural citizens, as per my old post: 'Democratizing Culture'. We don't need advertisers to impose cultural meanings from On High. So, my low opinion of them remains...