Amazon has filed patents for "Incorporating Advertising in On-Demand Generated Content." The technology will allow context-sensitive ads to appear on your kindle, perhaps in exchange for a lower price for your literature. One can imagine pages like this:

And Amazon is only one contributor to ever more pervasive advertising. Best Buy and TiVo are forming an alliance — Best Buy will heavily promote TiVo's set-top box, while TiVo will develop a box that will let the retailer advertise its offerings on TiVo subscribers' home TVs. Google continues to add to the capabilities it gives away for free, most notably by announcing that Chrome will become an operating system, potentially threatening Microsoft's ability to charge for Windows. But Microsoft is getting good feedback on Bing, its rival to Google, which bloggers think has potential to begin to replace the company's operating system revenue with ad sales. And new startups appear daily with the intent of attracting an audience for free content and adding advertising later.

One has to ask: how much advertising can an economy sustain?

Advertising once had an important informational function, letting buyers know what was available. And for a new movie, a new restaurant, or a new product, this function remains. But most of the expenditure on mass advertising today is for "share of voice," to make sure your brand isn't shouted down by its rivals. Yes, research has shown that advertising affects us more than we're aware — but does that influence make us buy more vodka, or simply shuffle share among the uncountable category of ever more super-premium brands?

There's a worrisome parallel with the world of finance. Originally, financial institutions provided credit to establish or expand businesses that created real value. When that business became so competitive that margins slipped, the industry competed to invent a set of games to play to keep themselves growing, resulting in the financial industry increasing its share of GDP without adding any real economic value to the economy.

The push for share of voice has created an arms race, where brands spend more and more to hold on their share of a slowly growing market. Like housing prices, this will sustain itself until someone — that is, the buyer — walks away from the table.

Could that moment be now? Observers are wondering if US consumers will ever return to their past spending habits. Since the last decade's growth has been attributed to the wealth effect — households feel richer even with a zero savings rate because their houses and financial assets make them money while they sleep — it makes sense to imagine an increased savings rate following catastrophic asset depreciation. Consumption will decrease, and in response, companies will...increase advertising?

Of course it makes sense that Google, Amazon, et al must create the capabilities that allow advertising to migrate from mass media to searched media. But the current explosion of advertising-supported businesses is leading to the next dot-com bust — only this time it will be ad-supported businesses, not e-commerce startups, that collapse.

Investments in new forms of advertising capability may be risky; that's not my point. The question is how much of a society's resources should be devoted to the arms race for eyeballs. Somewhere, there's a limit to what a slice of attention is worth.

Chris Meyer is part economist, part technologist, part futurist, and the founder of Monitor Talent, a part of the Monitor Group. He co-authored Blur, Future Wealth, and It's Alive. His articles have appeared in publications including the Harvard Business Review, the Sloan Management Review, Fast Company, Time, the Wall Street Journal, and BusinessWeek. For more, please visit his profile page at Monitor Talent. You can also follow Monitor Talent on Twitter.