Research firm Visiongain released a report today entitled Google in mobile and wireless: Analysing the impact and assessing the threat of the search giant's market entry.

The report states that Google's citywide wireless initiatives will increasingly pose a direct threat to U.S. mobile operators.

"The argument that Wi-Fi and cellular are complementary rather than competitive depends on who is operating the service," says report author Adam Walkden. "Google's successful advertising-based business model allows the company to offer services for free. If it can convert this business model to include local based advertising to Wi-Fi users, it poses a significant threat to mobile operators."