Twitter

Twitter was a social network in the 21st century.

History
In 2009, after the Torchwood Three team accidentally drove off the Severn Bridge, they heard a mysterious voice under the water. Back at the Hub, Ianto Jones stated that it was a hit on Twitter. (BBCR: Submission)

In 2011, a news reporter stated that "Miracle Day" had been "trending", terminology often associated with Twitter. (TW: The New World)

In the same year, Patricia Menzies said that her phone could not access Twitter. (BFA: The Crimes of Thomas Brewster)

When the Doctor's TARDIS arrived on Apalapucia and Amy Pond asked for her mobile phone, the Eleventh Doctor assumed she waned it to update her Twitter, rather than to take pictures of the sights. (DW: The Girl Who Waited)