Arnold also finds fault with Schmidt's public comments, which have sometimes fuelled existing controversies. And he notes that Google has had problems retaining talented employees, who sometimes leave to go to Facebook and more promising startups.

But while Google continues to generate most of its revenue from ads on its search result pages and partner websites, the company has spread its wings during Schmidt's tenure. It started by complementing its search service with other consumer online services, often rocking established markets, as it did with webmail when it launched Gmail in 2004.