2. Microsoft Buys aQuantive
Sale Price: $6 billion
Making a bid to play in the lucrative sandbox of Internet ad servicing, Microsoft payed more than it ever had for a company in order to acquire the digital marketing network aQuantive in 2007. With a $6 billion price tag, the move remains the priciest of its kind. aQuantive and all of its services were later re-branded and incorporated as a part of "Microsoft Advertising."