Facebook

Facebook was a social networking site. It connected individuals, and included a live video feature. (AUDIO: Aliens & Sex & Chips & Gravy)

The Sixth Doctor had an account, using the faces of his fourth, fifth, and current incarnations for his profile pictures. (PROSE: Academic Notes)

Donna Noble compared the Sub-Wave Network to an "outer-space" Facebook. (TV: The Stolen Earth)

According to Fester Cat, he had a Facebook account set up seemingly by 2007, which he used to interact with people far away. (PROSE: The Story of Fester Cat)

During the Atraxi incident in 2008, the Eleventh Doctor told Jeff Angelo to spread one word ("zero") across the whole world. Facebook was one of the methods of distribution that the Doctor suggested. (TV: The Eleventh Hour)

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 hit on Facebook. (AUDIO: Submission)

When the Twelfth Doctor mentioned that his sonic screwdriver had no effect on wood, Maebh Arden said that the trees could communicate with one another, if only just a little. The Doctor sarcastically asked Maebh if she thought the trees communicate by some form of tree-Facebook. (TV: In the Forest of the Night)

In a dream, the Twelfth Doctor told Clara Oswald not to get too attached to the people at the arctic base on the North Pole because it "isn't Facebook". (TV: Last Christmas)

In October 2016, Tanya Adeola killed time after homework by scrolling through some of Buzzfeed's lists. (PROSE: Joyride)

In 2017, Tyler Steele joked that Jack Harkness should have written inspirational quotes on his Facebook wall rather than taking up to a rooftop to deliver them. (AUDIO: Changes Everything)

As Adric recalled, the Fifth Doctor once described Facebook as a computer program which was banned on 21st century Earth for turning the Earth's population into "mindless, incommunicative zombies". (AUDIO: The Toy)

According to the Twelfth Doctor, Smartsuits could update Facebook pages. (TV: Oxygen)

Behind the scenes
The prequel for Doctor Who's ninth series, The Doctor's Meditation, was released in the United Kingdom on the official Doctor Who Facebook page.

Information from invalid sources
In a non-spoiler review of Big Show Everyone's Into, there were icons for Facebook, Twitter, Pinterest, and Reddit. (NOTVALID: Tom Baker stars in John Lloyd's lost Doctor Who adventure, The Doomsday Contract)