World-changing things that were mocked or feared when they arrived.
In Plato's Phaedrus, Socrates recounts the Egyptian king Thamus rejecting the invention of writing itself: "this discovery of yours will create forgetfulness in the learners' souls, because they will not use their memories; they will trust to the external written characters and not remember of themselves." Source: Phaedrus.
When the Byzantine princess Maria Argyropoulina arrived in Venice with golden forks, the clergy were scandalized (God had given man natural forks, his fingers), and when she died of plague soon after, it was declared divine punishment for her vanity. Forks took another six hundred years to catch on in Europe. Source: The sacrilegious fork.
The abbot Johannes Trithemius wrote In Praise of Scribes urging monks to keep copying books by hand, arguing that the word written on parchment would last a thousand years while the printed book, being paper, would quickly perish. To reach a wide audience, he had the treatise printed. Source: Johannes Trithemius.
As coffeehouses spread through London, an anonymous pamphlet, the Women's Petition Against Coffee, attacked "the Excessive Use of that Newfangled, Abominable, Heathenish Liquor called COFFEE," claiming it made men "as unfruitful as those deserts whence that unhappy berry is said to be brought." Source: Women's Petition Against Coffee.
When Jonas Hanway became the first man in London to carry an umbrella daily, crowds jeered him as effeminate and coach drivers, whose fares depended on rain, pelted him with trash; one tried to run him down. He carried it for thirty years and won. Source: Atlas Obscura.
The Quarterly Review, on the proposal to run trains at twenty miles per hour: "What can be more palpably absurd and ridiculous than the prospect held out of locomotives travelling twice as fast as stage-coaches!" Within fifteen years, trains were doing three times that. Source: Quote Investigator.
After Barthélemy Thimonnier won a contract to sew army uniforms by machine, an angry crowd of tailors, fearing the end of their trade, stormed his Paris workshop and destroyed the machines. He died poor; the sewing machine did not. Source: Barthélemy Thimonnier.
People so feared snapping hoist ropes that Elisha Otis stood on a raised platform at the New York Crystal Palace and ordered the rope cut with an axe. His safety brake caught the fall, and he announced: "All safe, gentlemen, all safe." Without it, no skyscrapers. Source: Elisha Otis.
Scientific American warned against the American chess craze: "chess is a mere amusement of a very inferior character, which robs the mind of valuable time that might be devoted to nobler acquirements," adding that "persons engaged in sedentary occupations should never practice this cheerless game." Source: Smithsonian Magazine.
Reviewing the Salon of 1859, the poet Charles Baudelaire declared that "by invading the territories of art, photography has become art's most mortal enemy," and called it "the refuge of every would-be painter, every painter too ill-endowed or too lazy to complete his studies." Source: Quote Investigator.
As cycling boomed across America, the medical press warned of "bicycle face." The Literary Digest described it in 1895: "usually flushed, but sometimes pale, often with lips more or less drawn, and the beginnings of dark shadows under the eyes, and always with an expression of weariness." The warnings were aimed disproportionately at women. Source: Women, beware of bicycle face!.
Vermont passed a red flag law requiring every self-propelled vehicle to have a person of mature age walk one-eighth of a mile ahead of it carrying a red flag to warn of its approach. Source: Red flag traffic laws.
John Philip Sousa, America's most famous musician, wrote "The Menace of Mechanical Music" against what he called "canned music," predicting "a marked deterioration in American music and musical taste," and that with machines singing for us, the human vocal cord would "be eliminated by a process of evolution, as was the tail of man when he came from the ape." Source: Smithsonian Magazine.
The Ladies' Home Journal published "Does Jazz Put the Sin in Syncopation?", declaring that jazz "disorganizes all regular laws and order; it stimulates to extreme deeds, to a breaking away from all rules and conventions." Source: Does Jazz Put the Sin in Syncopation?.
Psychiatrist Fredric Wertham's Seduction of the Innocent blamed comic books for juvenile delinquency. The US Senate held hearings, some American towns held public comic-book burnings, and the industry adopted the self-censoring Comics Code. Source: Seduction of the Innocent.
Ken Olsen, founder of Digital Equipment Corporation, then one of the most powerful computer companies on earth, told the World Future Society: "There is no reason for any individual to have a computer in his home." Source: Snopes.
Astronomer Clifford Stoll, in Newsweek: "The truth is no online database will replace your daily newspaper, no CD-ROM can take the place of a competent teacher and no computer network will change the way government works." On the prediction that we'd soon buy books and newspapers over the Internet: "Uh, sure." Source: The Internet? Bah!.
Microsoft CEO Steve Ballmer, laughing in a television interview: "Five hundred dollars? Fully subsidized? With a plan? That is the most expensive phone in the world. And it doesn't appeal to business customers because it doesn't have a keyboard." Source: 2007 interview (video).
Brian Chesky tried to raise $150,000 for the idea of strangers paying to sleep in other strangers' homes. He later published the replies: five investors passed, two never answered at all. The company is now worth more than most hotel chains combined. Source: Airbnb's rejection emails.
Four months after UberCab launched in San Francisco, the city's transit agency and the state utilities commission served it cease-and-desist orders, threatening fines and up to 90 days in jail per violation. The company dropped "Cab" from its name and kept driving. Source: TechCrunch, 2010.
Please send me more entries. (Preferably with sources.)