I signed up for Medium after reading this sentence in NiemanLab:
During an interview in April with top editors of The Pitt News student newspaper at the University of Pittsburgh, former New York Times executive editor Jill Abramson called Medium “an interesting new platform that has a lot of interesting blogger voices. A number of people on social media have sent me interesting links to its content. It seems to be getting traction from what I can see. Tumblr was kind of, for a while, some years ago, the ‘it’ blogging platform, and now it seems like Medium is.”
So, hello, ‘it’ blogging platform!