4. Google Apps $1.03 Billion (analyst estimates)
CEO: Larry Page
According to Baird Technology Research analyst Colin Sebastian, cloud services such as Google Apps are "right up Google's alley." Online email, calendar and documents are seen as fitting nicely into the company's service portfolio, but it's also true that these efforts have attracted the attention of Microsoft, which has responded with its "Scroogled" marketing campaign, aimed at generating fear, uncertainty and doubt around the extent to which Google is looking over the shoulders of users and using the data for marketing purposes.