To promote the launch on Wednesday of the first Android-based mobile phone, Google has provided T-Mobile with advertising that money just can't buy.

Google has added the following text to its U.S. home page: "New! The G1 is on sale now. Learn about the phone."

Those last four words link to a landing page that belongs to Google. On that page there's a banner that reads "Experience the T-Mobile G1" and leads to the T-Mobile site when clicked.

T-Mobile did not respond to a request for comment on the effectiveness of Google's promotion. Google declined to provide information about how many users were clicking through to the landing page or the T-Mobile site.

Google has promoted its own products and services, like its Chrome browser, with links on its home page before. The first non-Google product featured on the Google home page was Mozilla's open source Firefox browser, in April 2006.

If you count Firefox as a quasi-commercial product -- it is distributed by the for-profit Mozilla Corp., a subsidiary of the nonprofit Mozilla Foundation -- the T-Mobile G1, manufactured by HTC, appears to be the first commercial product to be promoted on the Google home page.

But that's not how Google sees it. For Google, the G1 is not a third-party product. "We see T-Mobile's G1 as a Google product since our platform is embedded on the phone, and we promote Google products on our home page when we feel it's useful for users," a Google spokesperson explained via e-mail.

Google's home page is generally on a restricted-calorie diet. Over the summer, when privacy advocates called for Google to add a link to the company's privacy policy on its home page to comply with California law, Google resisted, in part to avoid adding text that might slow the page's load time and degrade the user experience.

Eventually, when Google relented, Marissa Mayer, VP of search products and user experience, in a blog post explained that Google co-founders Larry Page and Sergey Brin "told me we could only add [a privacy policy link] to the home page if we took a word away -- keeping the 'weight' of the home page unchanged at 28."

As far as Google is concerned, promotions represent temporary indulgences that don't affect the Google page weight. "We are currently running a home page promotion," a Google spokesperson explained. "These promotions appear when we launch a major product or service that users might be interested in, or to support a cause that users care about, including the May Sichuan earthquake relief efforts. Because these promotions appear on our home page for only a few days at a time, we don't consider them in our official home page word count."

Were Google ever to commit to commercializing its iconic white home page, there would be both rewards and risks. Certainly, the company could earn significant revenue or advance its technological agenda by allowing advertisements on one of the most prominent pages on the Internet. Some Google watchers have speculated it's only a matter of time before that happens. And given the nature of the economy at the moment, the pressure to please investors might push Google in this direction.

But the appearance of ads on Google's home page could, fairly or unfairly, undermine the company's reputation as a neutral provider of search results by implying a preference for industry partners or advertisers.

As someone commenting under the name "Justin" on the Google Operating System blog said, "I think this is dangerous. Google has a reputation of being non-biased. They have, in the past, promoted their own products. They have also mentioned nonprofit third parties. But I don't like the fact that they're promoting T-Mobile on their home page."

Of course, as Google sees it, G1 stands for Google.