Google Labs has launched Voice Local search. It automatically connect a user with local businesses in a particular area.
TechCrunch informs: "Goog-411 can be accessed by dialing 1-800-GOOG-411. The product is completely automated and there is no way to talk to a human for additional or clarifying information. You tell it your city and state, and then ask for a specific business or business category. In my tests the product was excellent. Although the voice recognition was only working at about 70% efficiency, I just said “back” and retried when it didn’t understand what I said. Results are spoken back or text messaged back to you, and you are automatically put through to the phone number requested."
Goog-411 is primarily making use the information that is openly available on Google maps. They might refer other sources as well. A business house or merchant can also add themselves.