AdMob, that really took off after its acquisition in 2009 by Google, Inc. Over the years, some of the largest mobile ad networks were acquired by other major players in the field, like, for instance Flurry and BrightRoll by Yahoo, MoPub by Twitter, Millennial Media, Adap.tv by AOL and LiveRail by Facebook. At the same time, certain top mobile ad networks remained independent, like Chartboost, InMobi, Smaato, StartApp and TapJoy.