Blogging platform Tumblr is maintaining its sharp growth, announcing yesterday that it had notched up the 20 billionth post from its users on Monday night. More than 50m posts are being created every day on Tumblr blogs, of which there are now more than 49.7m. That’s up from 20m in June 2011, meaning it has added 39.7m in the last nine months alone. Its last announced posts milestone was 12bn in November 2011, so engagement with its platform is accelerating too. Numerous artists are now using Tumblr in addition to Facebook, Twitter and their own sites.