Google made a $700 million bid for ITA, which compiles flight information for airlines, travel agencies -- and rival search engines. The bid garnered complaints from competitors who rely on ITA's service, but the feds eventually approved it with conditions.
#3: AdMob mobile advertising, $750 million
Android is all about increasing mobile search usage today, but Google hopes to make mobile advertising in general into a huge business. That's why it paid $750 million for AdMob in November 2009. Since then, however, AdMob execs have left -- including former CEO Omar Hamoui (pictured here) -- and sources have said the integration isn't going so well.