It's one small step for Google engineers, and one, well, pretty big step for advertising: RCR Wireless News reports that Google has expanded its AdWords advertising marketplace to mobile devices.

What does this mean? As more and more people whip out their cell phones to Google the location of the nearest steakhouse or car wash, AdWords advertisers' messages will be front and center, and very likely geographically targeted over time - though there is no evidence that the initial offering has geo-targeting capability.

The Google Operating System blog notes that the mobile ads are simply a stripped-down version of those that would appear on a normal Web search: "When a user searches Google.com from a PC for your keywords, your standard text ads will appear alongside the search results. And when someone uses a mobile phone to search Google.com for your keywords, your mobile ads will appear."

Google has for some time offered a cell-phone-optimized version of its search engine, but without ads until now. RCR describes the launch as "quiet," coming without fanfare after an April launch of the service in Japan.

The move into mobile advertising clearly calls out for an implementation of "click-to-call" ads, which Google has just started exploring with eBay. And all of this suggests Google will continue to maintain its technological lead in the hot search-ad market over Yahoo and Microsoft's nascent search-ad effort.