A number of conspiracy theories surround the deaths of some on the world's most dangerous former leaders.

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Yes, they really are out to get you.

Despite their widespread appeal, conspiracy theories have a bad reputation.

From 9/11 and JFK to the moon landing and Jeffrey Epstein’s death, people who question the official explanation are often branded crazy.

These days, peddling conspiracy theories on YouTube can even get you banned.

So it doesn’t help to find out that the CIA really did have a secret mind-control program, or that the US government recruited Nazi scientists after World War II and plotted “false flag” terror attacks on its own people.

Here are some of the conspiracy theories — or just plain old conspiracies — that really did happen.

THE PHOEBUS CARTEL

As the old saying goes, “They don’t make them like they used to”.

While it’s a cliche that products today aren’t made to last — from iPhones and ink cartridges to cars and washing machines, everything seems to have a built-in expiry date — it’s not your imagination.

The technical term is “planned obsolescence”, meaning products are deliberately designed with an artificially short lifespan.

That can either be achieved by intentionally using materials that will break down faster, denying repairs, or other gimmicks like non-replaceable batteries.

With the advent of technology the practice has become even more blatant.

One example is software lockout, where developers force users to upgrade to newer versions by pulling support and compatibility with older ones.

Another is programmed obsolescence. Last year, HP reached a $US1.5 million ($2.9 million) settlement in a class-action lawsuit that alleged it designed its printers and cartridges to shut down at an arbitrary expiration date.

General Motors is widely credited with starting the practice in the 1920s, enticing consumers to regularly purchase the latest model with yearly updates to colours and styles.

But while the car maker was open about its intentions, at around the same time there was a genuine conspiracy to introduce planned obsolescence — to light bulbs.

In December 1924, the world’s biggest light bulb manufacturers met in Geneva to form the “Phoebus Cartel”, carving up the international market among themselves.

As the IEEE Spectrum magazine noted, while the cartel itself only lasted until the 1930s — and its existence wasn’t uncovered until decades later — its real legacy was the introduction of a shorter lifespan for light bulbs.

Prior to 1925, light bulbs typically lasted around 2000 hours. The cartel managed to halve that to just 1000.

Given the world’s longest lasting light bulb, The Centennial Light, has been burning for nearly 120 years, consumers have a right to be annoyed.

“This cartel is the most obvious example (of planned obsolescence’s origins) because those papers have been found,” Giles Slade, author of the book Made to Break, told the BBC in 2016.

SECRET UFO PROGRAM

In the 1940s and ’50s, the US was gripped with UFO hysteria after a wave of unexplained sightings of “flying saucers”.

In response, the US Air Force was tasked with investigating the phenomenon. Project Blue Book, launched in 1952, looked into 12,618 UFO sightings reported between 1947 and 1969, ultimately finding that 701 remained “unidentified”.

Still, the air force declared “case closed” and the program was shut down.

In the nearly five decades after the end of Project Blue Book, the US government’s official position was that it no longer investigated UFOs.

That is until December 2017, when The New York Times revealed the existence of a secret Pentagon program called the Advanced Aerospace Threat Identification Program.

The program itself was tiny — $US22 million ($32 million) is barely a rounding error in the US Defense Department’s annual budget of more than $US600 billion ($876 billion) — and the Pentagon said it was discontinued in 2012.

But it was the first time the US government had officially acknowledged it was still studying UFOs in nearly half a century.

The former head of the AATIP program, Luis Elizondo, insists it is still ongoing. Mr Elizondo now works with Blink-182 rocker Tom DeLonge’s UFO research group To The Stars Academy.

While some doubts have been raised about his claims, he was responsible for the release of three UFO videos taken from fighter jets.

Earlier this year, the US Navy, which had previously kept quiet, caused a stir when it confirmed the three videos were genuine and depicted “unidentified” objects.

That came after it issued new classified guidelines on how to report such sightings “in response to unknown, advanced aircraft flying into or near Navy strike groups or other sensitive military facilities and formations”.

John Greenewald Jr, who publishes The Black Vault, told Motherboard he was surprised at the language the Navy used in its official statement.

“I very much expected that when the US military addressed the videos, they would coincide with language we see on official documents that have now been released, and they would label them as ‘drones’ or ‘balloons’,” he said.

“However, they did not. They went on the record stating the ‘phenomena’ depicted in those videos, is ‘unidentified’. That really made me surprised, intrigued, excited and motivated to push harder for the truth.”

OPERATION MOCKINGBIRD

The CIA used to control the media — but don’t worry, it doesn’t any more.

It’s probably won’t come as a surprise to many to know that journalists and news organisations worked “hand in glove” with the spy agency to push propaganda for decades after World War II.

The program was started in 1948 under CIA official Frank Wisner but only came to light in the 1970s after the Watergate scandal prompted congressional review of domestic surveillance activities.

In 1977, investigative journalist Carl Bernstein published an explosive, 25,000-word story in Rolling Stone detailing the CIA’s extensive tentacles into the world’s most powerful media organisations.

According to Bernstein, the CIA even ran a formal training program in the 1950s to teach its agents to be journalists with officers “taught to make noises like reporters”.

“These were the guys who went through the ranks and were told, ‘You’re going to be a journalist’,” a CIA official said.

Virtually every major publisher including The New York Times, The Washington Post, Newsweek, Associated Press, Reuters and broadcasters including CBS, ABC and NBC took part in the program.

“You could get a journalist cheaper than a good call girl, for a couple hundred dollars a month,” a former CIA agent told journalist Deborah Davis in her 1979 biography of Washington Post owner Katharine Graham, Katharine the Great.

According to Davis, the program was called “Operation Mockingbird”, although that name doesn’t appear in official CIA documents.

In later declassified materials the agency did acknowledge a “Project Mockingbird”, which involved spying on journalists in the 1960s.

When George H.W. Bush took over as head of the CIA in 1976, he announced a new policy.

“Effective immediately, the CIA will not enter into any paid or contractual relationship with any full-time or part-time news correspondent accredited by any US news service, newspaper, periodical, radio or television network or station,” he said.

But, as Bernstein wrote, “The text of the announcement noted that the CIA would continue to ‘welcome’ the voluntary, unpaid co-operation of journalists. Thus, many relationships were permitted to remain intact.”

frank.chung@news.com.au