Last week, Elon Musk dashed off 125 characters announcing a remarkably ambitious plan to send Amtrak to an early grave. “Just received verbal govt approval for The Boring Company to build an underground NY-Phil-Balt-DC Hyperloop. NY-DC in 29 mins,” he proclaimed in a tweet.

Ricki Harris is Backchannel’s editorial fellow. Sign up to get Backchannel's weekly newsletter.

Yet something about this particular moonshot seemed off. To begin with, “verbal government approval,” as politicos noted, doesn’t really exist. Receiving actual approval for a multibillion-dollar nationwide transportation system would require quite a few things: a stamp of approval from the Department of Transportation, agreements from and between the local governments for all cities involved, a plan for navigating regulations, permits, and, last but not certainly not least, the money. We should also mention that—oh, yeah—Musk’s much-lauded hyperloop technology doesn’t actually exist yet.

But Musk’s declaration is just the latest too-good-to-be-true pledge from the tech world. In the industry of innovation, unfulfilled promises have a long history. For decades, Silicon Valley has been imagining the future and pitching it to us as the definitive image of tomorrow. Musk himself is responsible for a number of outlandish promises—like his plan to beat extinction and bring a million people to Mars, or his talk of a suborbital spaceship that, by 2020, will make most places on Earth no more than 25 minutes away. (To be fair, Musk did some cool promise keeping with Tesla and SpaceX.) Yet these titans are remarkably quiet when it comes to part two of a sky-high promise: actually making it happen.

In most industries, unachievable promises are a sign of bad leadership. But in tech, where companies are built on impossible ideas, unreasonable pledges are just a part of doing business. It’s even written into the Valley's unofficial motto: Fail fast, fail often. But why do our best and brightest get away with overly optimistic claims that fail to materialize, time and time again?

To put this latest instance of hoopla into perspective, we’ve compiled a list of the bold promises on which we’re still waiting for Silicon Valley to deliver.

1. Bill Gates and the Eradication of Spam

Promise: Junk mail getting you down? Fear not. “Two years from now, spam will be solved,” Bill Gates assured participants at the World Economics Forum. Just one problem: He made that promise in 2004. At the time, Gates had a few ideas for how to stamp out computer-aided mass mailers: a puzzle that could only be solved by a human, a computational puzzle that only a computer sending a small number of emails could handle, or hitting spam senders with a fee.

Reality: Go ahead, check your inbox.

In the 13 years since we were promised a spam-free life, other services have stepped in and attempted to make good where Gates did not. For a while, the app Unroll.me, which bundled mass mailings into an easy-to-read digest, seemed like the answer—until it turned out to be yet another ploy for your data.

2. Sebastian Thrun and MOOCs

Promise: In 2012, former Stanford computer science professor Sebastian Thrun assured the world that we were overdue for a higher education culling. After he attracted 100,000 students to his experimental online course at Stanford, Thrun left that post to found the online education startup Udacity, where he sought to offer an inexpensive, high-quality college education to anyone with an internet connection. In 50 years, he told WIRED, there would be only 10 institutions in the world delivering higher education—and Udacity could be one of them. Say goodbye to college loans: MOOCs (Massive Online Open Courses) were the future.

Reality: MOOCs are still around, but they’re hardly dominating the higher education scene. The first problem: MOOCs, which often partner with elite universities, rely heavily on the prestige of the same institutions that their proponents claim are antiquated. The supposed MOOC revolution has also failed to take into account the social benefits of attending college outside of your living room. In 2015, the Daily Dot noted that only 15 percent of enrolled students completed their MOOC degrees, and that the majority of those enrolled already had college degrees. Today, MOOCs are more commonly viewed as a supplement to a traditional college education, rather than a substitute.

3. Larry Ellison and the Network Computer

Promise: One year after the Windows 95 craze, Oracle released the computer that was supposed to unseat Microsoft. The Network Computer was a simple, relatively inexpensive machine that stored data online, eliminating the need for a massive hard drive. Oracle CEO Larry Ellison viewed the no-frills Network Computer as the first step in driving down the cost and complexity of household computers. “We think these machines will dramatically outsell Windows in a short period of time,” Ellison told the Mercury News at the time.

Reality: Four years and $175 million dollars later, Oracle called it quits. From a business perspective, the NC was an indisputable product failure. But from an industry perspective, Ellison was onto something. As he predicted and as we now know, the market was eventually flooded with cheaper, simpler computers that chipped away at Microsoft’s monopoly.

4. Dean Kamen and the Segway

Promise: In December of 2001, Dean Kamen unveiled his masterpiece—the Segway—a mode of transportation that the inventor assured us was the next step in the transit revolution. The Segway, Kamen told Time, “will be to the car what the car was to the horse and buggy." Within a year, he assured the reporter, a shift would be well underway, with Segways dominating the sidewalks of major cities across the world.

Reality: The silver screen’s favorite mall cop, Paul Blart, is perhaps the only one of us to have experienced Kamen’s revolution. (Along with the throngs of tourists clogging up the streets on Segway tours.) The Segway’s failure was a matter of accessibility and practicality: At $5,000, it was far too expensive for most Americans, and at 100 pounds, it was inconvenient to keep with you for the day. And of course, there was the wave of bad press—most memorably, President George W. Bush’s tumble.

5. The RAND Corporation and Digital Medical Records

Promise: In 2005, the future of digital medical records seemed bright. Researchers at the RAND Corporation predicted that doctors would swiftly ditch their manila envelopes and filing cabinets. The increased efficiency and safety would save the healthcare system $81 billion annually.

Reality: RAND’s $81 billion estimation was tied to the projection that 90 percent of doctors would quickly ditch paper. Not so. Doctors were not quite so eager to digitize: By 2016, only 75 percent of doctors had adopted electronic medical records. Even today, digital records present a few obstacles. For starters, the system is spread across multiple companies that have a history of blocking information and access to records from one another (though as of 2016, companies have agreed to stop this practice). And doctors have reported difficulty with the technology, which isn’t particularly user friendly. What’s more, some researchers have suggested that the technology actually increases health care costs, because it makes ordering an expensive test as easy as clicking a button.

6. Jeff Bezos and Drone Deliveries

Promise: In December 2013, Amazon revealed a plan to launch speedy delivery into the air. On an episode of 60 Minutes, Jeff Bezos debuted delivery drones that could carry packages of up to five pounds as far as 10 miles. Delivery time, he estimated, would be cut to 30 minutes. Bezos predicted a rollout beginning in 2015, at the earliest.

Reality: It’s 2017 and we’re still waiting. Amazon Prime purchases still aren’t delivered via drone—but Amazon hasn’t given up on the idea, either. In March, Backchannel witnessed the first public test delivery, a service that Amazon is still dead set on implementing. Cool as it may be, drone delivery service is still in test phase. For now, the wait continues.

7. Elon Musk and Telepathy

Promise: Elon Musk has promised us so many things. Among the most outrageous is the arrival of computer-aided telepathy. In April, Musk announced that his new company, Neuralink, would take brain-machine interface to the next level, allowing people with implants to communicate without talking. Physical disability, he said, could be all but wiped out in four years, while full-on telepathy would take some eight to 10 years to accomplish.

Reality: Musk is just one of a wave of tech titans working on brain machine interfaces to enhance cognition. Facebook, for one, is also working on an interface to increase the brain’s power. Though the idea may be sound, the timeline is absurd: Expert after expert has advised that telepathy tech will take decades, at best, to build.

8. Anthony Atala and 3D Printed Organs

Promise: In 2011, Dr. Anthony Atala took to the stage at TED and printed off a kidney using a 3D printer. The surgeon even brought out a patient who had received an engineered bladder a decade earlier. Though the timeline was fuzzy, the technology was engrossing. By creating new organs from a patient’s own cell tissue, Atala explained, he could someday narrow the gap between the number of organ donations needed and the number of organs available.

Reality: Someday turned out to be a little farther away than expected. Atala and his team at Wake Forest University are still hard at work perfecting the technology around 3D-printed organs. His lab isn’t churning out 3D-printed kidneys yet, but as of December 2016, Atala reported that printed bone and muscle tissue had been successfully implanted in a rodent.