Google's AdSense has proven really profitable. The contextual advertising service helped the Internet recover from the tech bust, showing that offering free content can make money. Now, the company seeks to expand its efforts to repeat its success in the mobile world.

Google is expanding its mobile ad trial from the US, UK, Germany, and Japan. It's including eight more countries. CEO Eric Schmidt dreams of the day when mobile advertising will make handsets free.

This is just another development involving one of Google's many mobile initiatives, which include offering GMail and Google Maps to smartphone users.