These are all estimates from this article: http://business.time.com/2013/05/21/inside-yahoos-tumblr-deal-heres-who-hit-the-billion-dollar-jackpot/ http://busine

These are all estimates from this article: http://business.time.com/2013/05/21/inside-yahoos-tumblr-deal-heres-who-hit-the-billion-dollar-jackpot/ http://business.time.com/2013/05/21/inside-yahoos-tumblr-dea... Which in turn got them from a company called PrivCo: http://www.privco.com/ http://www.privco.com/ Who knows how accurate they are.