Not all great ideas become great inventions. And even ones that are actually great products can easily be ousted by better marketed products, or products that are better funded by bigger outfits. There have been many technological successes and failures in recent history, here are some of the biggest failures or flops:
The Apple Newton
This was Apple's idea of a mobile device, similar to what Palm was offering. It was plagued with software issues and was REALLY expensive, over $700! (remember this was in the 90's).
Nintendo Virtual Boy
The worst thing that Nintendo has ever released. It was basically a pair of goggles that sat on a tripod on your desk. The screen you looked at consisted of two colors: black and red, and supposedly gave you a "3D Experience".
Cuil Search Engine
Supposedly a "Google Killer", hardly. The creators blew through tens of millions of dollars creating the thing, and a couple of years into it, they shut it down. Why did it fail? Because it's not Google, and came nowhere near even putting a scratch, let alone a dent into it.
Although a very cool and fun console, it came out too early, was too expensive, and was one of the easiest consoles in the history of gaming consoles to pirate games for.
It was actually better than windows at the time, and much more advanced. Unfortunately not marketed correctly. Combine that with IBM and Microsoft working on it jointly and neither company putting enough dollars into it, and Microsoft working on Windows at the same time, and you have a recipe for disaster.
The Joojoo tablet
It was originally going to be called the "CrunchPad", and a joint venture between tech-blog TechCrunch and an Indian hardware firm. Not 100% on the story, but it seems that the two parties had some ownership issues and the Indian firm went rogue.
Before it was released it was touted by the inventor Dean Kamen that it would change the world. Code named "Ginger", it ended up being an overpriced scooter that balances on two wheels with gyro stabilizers.
It was touted as something to release the program manager within windows, and in a nutshell create a simpler and easier to use user interface for windows. It bombed, big-time, and it to this day viewed as one of the worst products Microsoft has ever released.
Sony's MiniDisc was a new media format that looked kind of cool and futuristic at the time, but ended up becoming a media that nobody bought. The minidisc players were too expensive as were blank discs. Not to mention that the first MP3 players came out at pretty much the same time, so it was a no brainer to get one of those instead.
This was Microsoft's response to the iPod. Although technically a decent device, it was ugly, not well marketed, and basically nowhere near the quality or league that the iPod was in at the time it was released.
This was actually a superior technology to VHS when it was first released, and for a while owned almost the entire market. But when VHS came along it offered almost double the amount of time that could be recorded on tapes, and won the battle over Betamax. Then when superVHS came along enhancing the technology it destroyed the competition.
This version of Windows, often referred to as "Mistake Edition" has been criticized as the worst version that Microsoft has ever released. It's a really stripped down version of Windows that tends to be very unstable and crashes a lot. It's even been reported that Microsoft has apologized for releasing it.