In its recent "BrandZ 100 Most Valuable Global Brands Ranking," Milward Brown Optimor, a market research company, declared that Google (GOOG) is the most valuable brand in the world. Citing a valuation of just over $100 billion, the ranking placed it ahead of Microsoft (MSFT), Coca Cola (KO), IBM (IBM), McDonald's (MCD) and dozens of other internationally-recognized favorites.

Milward Brown's valuation is based on the revenues that it assumes the companies will earn over the course of their existence. In this context, the valuation of Google is particularly interesting. As ubiquitous as it has become, the search behemoth doesn't behave like most mega-brands. Unlike Coke or Tide or Lucky Charms, it doesn't sell tangible products.
Admittedly, Google has a great ad plan, and its constant online auction model means that it can offer relatively cheap, prominent ad placement that is carefully targeted to users. However, while it seems likely that Google's ad model will become the method of choice for many online marketers, it is still unclear how, exactly, it has propelled the brand ahead of Microsoft, Apple, and the hundreds of other brands that have wormed their way into the hearts of billions of consumers.

Of course, taken to an extreme, BrandZ's statement that its valuation is based on future earnings opens a lot of doors for creative accounting. After all, with Google gaining access to most of the world's printed text, there seems to be little limit to how much power and money it will be able to generate. What's more, as the world's preeminent aggregator of information, Google will have -- and arguably has -- the ability to make or break thousands of other brands.

On the other hand, as we work our way toward a dystopic future in which the Google logo is branded on everyone's forehead, the company's revenue model seems to be on a narrow -- and somewhat uncertain -- footing. According to BrandZ, Google "owns 73 percent market share" in the online search advertising arena. However, as the publishing industry is discovering, ad revenue may not be enough to guarantee a secure future. Moreover, given that both the "demand" that Google exploits and the "product" that it sells are external, it seems entirely too dependent upon market forces that it cannot control.

In other words, while Google undoubtedly has a promising future, it seems a little early to bet the farm on it.