SAN FRANCISCO - Google doesn't charge its carrier, OEM, and developer partners a dime for its mobile operating system, but apparently the search giant is still making money in the mobile space. During a wide ranging talk at the D: Dive Into Mobile Conference, Google's vice president of Mobile Platforms, Andy Rubin, explained that the advertising on Android-based phones is a revenue stream for the search giant and, in fact, makes the Android enterprise within Google profitable all by itself.

Rubin didn't go into great detail about how Google makes advertising money on the Linux-based platform, but he did explain that even on phones where users do not have the Google search bar pre-installed (some carriers swap Bing for Google), a large number of people still type in Google.com to search on their phones, driving organic search on these Android phones, and returning Google search results which, of course, feature Google-driven contextual ads.

When asked about the still sometimes clunky nature of the Android mobile OS, Rubin said he still sees Android as an early adopter platform built for tech enthusiasts, but expects that situation to improve with the introduction of the .

There are now, according to Rubin, 172 different phone SKUs offering Android, many of them modifying the interface and swapping in and out Google features and various propriety pieces of mobile software. Rubin said that this is the reality of offering an open platform. One host wondered if Android is becoming the "Microsoft of mobile phones," where partners take the OS and build whatever they want around it and put whatever software they want on the hardware. Rubin countered with "We're probably more like the Linux of phones," a comment he almost instantly regretted.

Rubin also talked about the competition, and was generally complimentary to Apple, saying the company learned from its mistakes and that they "make great consumer products." In fact, he said the iPhone and Android share a distinct advantage: They're both new. Starting with a clean slate is, Rubin explained, a definite advantage. He then compared it to Windows Phone 7, which Rubin contends is built on 20 year-old Windows Mobile 1 code.

There was some praise for Microsoft's latest mobile accomplishment. Rubin likes the tiled screen and called Windows Phone 7 "a good 1.0 product."

Rubin also had some interesting advice for BlackBerry manufacturer RIM. "What did [Motorola's] Razr do? It faded away. So what did Motorola do? Switched to Android."