7. Bartłomiej Brzozowiec made a bug report arguing that Firefox shouldn't connect to Google safe browsing API and set a special cookie because of privacy concerns. His concerns were rebuffed by responders including a Google employee. Years later Snowden leaks revealed that the NSA used this cookie to track people.
8. Italian chemist Amedeo Avogadro's theory that "equal volumes of gases at the same temperature and pressure contain the same number of molecules regardless of their chemical nature and physical properties", wasn't accepted until nearly 50 years later. It is now one of the fundamental principles of analytical chemistry.
9. Harry Markopolos figured out Bernie Madoff's scheme before anyone else. He sent information about the scheme to the Securities and Exchange Commission 5 times before being taken seriously.
"It took me five minutes to know that it was a fraud. It took me another almost four hours of mathematical modeling to prove that it was a fraud."
10. Back in 1991, Defense Secretary Dick Cheney had a very different opinion on entering a war with Iraq. He believed that toppling Saddam was a bad idea because it would lead to a quagmire which pit Sunnis, Shias, and Kurds against each other, and which the US would get stuck sorting out. Unfortunately, he didn't listen to his own prediction.
11. Stanislav Petrov, a colonel of the Soviet Air Defence Forces, prevented World War III. He didn't believe a nuclear early-warning system when it had reported that multiple missiles had been launched from the USA. He suspected the system was malfunctioning, and decided to not report what he saw.
It was later determined that indeed the system malfunctioned, and had he reported what he saw, a nuclear response from the USSR was highly likely.
12. Ignaz Semmelweis, a Hungarian physician, introduced the ideas of doctors washing their hands before delivering babies. He argued hand washing could reduce infant mortality to below 1%. This lost cost him his medical license. Only years after his death did Louis Pasteur, a french microbiologist, confirm Semmelweis' germ theory.