In its second-largest acquisition, Amazon buys the company for $970 million.
Mobile accounts for nearly a quarter of consumers' paid search clicks.
Mobile is taking a bigger share of the paid search pie. Search engine marketing firm Marin Software Inc.'s U.S. clients saw their share of Google paid search clicks from mobile devices rise from 14.2% in 2011 to 23.4% last year, the firm says. In that same period, advertisers increased the share of their search budgets designated for mobile devices from 10.0% to 18.4%.
The average paid search ad click-through rate for Marin Software's U.S. clients in 2012 was 2.28% on desktop computers, 4.72% on smartphones and 3.12% on tablets, Marin reports.
The average paid search ad cost per click for Marin's U.S. clients in 2012 was 75 cents for desktop computers, 48 cents for smartphones and 62 cents for tablets.
The average paid search ad conversion rate for Marin's U.S. clients in 2012 was 3.9% on desktop computers, 2.8% on smartphones and 3.3% on tablets.
"It's important to note that conversion rates for tablet devices are improving relative to desktops and smartphones," the company says. "During 2012, tablets saw a 31% increase in conversion rates, compared to 9% for smartphones and 7% for computers."
Though smartphones underperformed on conversion rates, more research is warranted on their role in paid search, the marketing firm says.