From
https://venturebeat.com/2015/04/13/why-the-ad-tech-industry-…
August 2013: Millennial Media acquires Jumptap for $225 million (mostly stock).
September 2013: Twitter acquires MoPub for $350 million.
January 2014: Facebook acquires LiveRail for $500 million.
May 2014: Google acquires Adometry for an undisclosed amount.
July 2014: Yahoo acquires Flurry for between $200 and $300 million.
August 2014: Rocket Fuel acquires [x+1] for $230 million.
September 2014: Millennial Media acquires Nexage for $108 million.
November 2014: Yahoo acquires BrightRoll for $640 million.
March 2015: Rubicon Project acquires Chango for $122 million.
March 2015: Flipkart acquires AdIQuity for an undisclosed amount.
March 2015: Cheetah Mobile acquires MobPartner for $58 million.
March 2015: AppNexus acquires Yieldex for $100 million.
March 2015: Rumors of Google acquiring InMobi
Anirban