Also see Exclusive: Automattic CEO Matt Mullenweg on what’s next for Tumblr | The Verge
"Thus, it quickly got its lofty valuation with $125 million in investments from tech’s smartest investors and took off. It hit a billion blog posts by 2010, and when the site started accepting advertising in 2012, Tumblr seemed golden.Who Killed Tumblr? We All Did
Fool’s gold. What plagues the internet today hit Tumblr hard and early. There were the inevitable copyright problems and spam and security problems and product problems. And the content itself, which started as edgy, got rather gnarly, from self-harm sites to neo-Nazis to what really tanked Tumblr: sex.
The very fast growth of sites that were soon deemed pornographic got to be a too large part of the site, a development that got a lot of attention in the frenzy of the Yahoo purchase. While some of those blogs were seen as safe havens to explore sexuality, there was too much hard-core pornography — and that did not fly in a corporate setting."