Twain dreamed up an invention called the "telelectroscope," which used the phone system to create a world wide network of information-sharing. Basically, Mark Twain invented the Internet. Keep in mind that he wrote this in 1898, when telephones were still fairly new and rare.
But Twain didn't stop there. His story describes "the daily doings of the globe made visible to everybody, and audibly discussable too, by witnesses separated by any number of leagues." Mark Twain is talking about goddamn social networking. He didn't just predict that the Internet would unite the world, but also that people would immediately clog it up with trivial bullshit.
"Day by day, and night by night, he called up one corner of the globe after another, and looked upon its life, and studied its strange sights, and spoke with its people. ... He seldom spoke, and I never interrupted him when he was absorbed in this amusement."
Sorry. I'll go do something useful now.