Google is moving deeper into the travel business. It now review hotels and restaurants via Zagat and is expanding ties with big hotel groups like Hilton Worldwide. Google has also sealed a licensing deal with hotel booking software startup Room 77 to help with its travel booking efforts. The major questions is, will Google play nice with its advertisers? Priceline and Expedia together pay a combined $2.5 billion every year to advertise on Google, or about 5% of Google's ad sales.