Google may use a user-driven rating system to help keep bad or harmful Android applications off mobile phones.

The search giant is in talks with mobile operators about offering phones based on its Android open-source platform, said Rich Miner, group manager of mobile platforms at Google, in an interview at the AlwaysOn Stanford Summit on Wednesday. However, the carriers want reassurance that users won't install troublesome applications, Miner said.

Google is making Android freely available to developers under the Apache open-source license and not restricting what they build with it. The company says its aim is to establish a common software platform for many handsets and help make mobile applications proliferate. In much of the world, software for mobile phones traditionally has been supplied through carriers after laborious reviews and modifications.

Mobile operators are concerned primarily about two types of applications, Miner said: ones that can harm phones, the network, or subscribers' personal data, and ones that are buggy or frustrating to use. They are concerned the latter will generate a high volume of calls to the carrier for support, he said.

Google won't compromise on letting Android developers offer their applications without prior approval. "We're not going to have an app-signing hurdle," Miner said.

But in a bid to discourage users from installing bad applications, Google may use a rating system similar to the one on its YouTube video site. There, viewers can rate each video with a certain number of stars.

If users of Android phones found applications with low star ratings, they would tend not to download them out of self-interest, thus reducing the impact of any bad applications that become available, Miner said.

Also borrowing from YouTube, Google could act to remove applications or services that violate copyright, Miner said. In a system that has come under fire from YouTube users and copyright owners alike, Google can remove videos from the site in case of complaints of copyright infringement.

Providers of open application platforms seem to be grappling with how to police the quality of software. Also on Wednesday, Facebook announced its Facebook Verification program in the wake of a flood of new applications being offered to users of the social-networking service. Starting in September, developers will be able to submit their applications to Facebook for verification that they meet certain criteria for trustworthiness, the company announced at its f8 developer conference in San Francisco. The company will also recognize what it considers the very best Facebook applications through a program called Great Apps.

Even Apple, which more tightly controls iPhone applications offered on its AppStore, has a star-based user rating system.

After Android phones hit the market, which Miner said is on track to happen in the second half of this year, some may come through mainstream carrier channels, including with price subsidies, according to Miner. As for carriers agreeing to let subscribers download any Android application, Miner said they are "getting there."