* There's an obviously good idea, people have tried it and "proved" that it cannot be done. Then somebody ignorant of this fact goes ahead and does it anyway. A famous example of this is Spencer Silver of 3M inventing the adhesive for the Post-It notes. He is quoted to say "If I had thought about it, I wouldn't have done the experiment. The literature was full of examples that said you can't do this."
* There's a good idea, others have implemented it with modest success. Then somebody comes along and blows it out of the water. Best example I can think of for this is the iPod. MP3 players were common before Apple, so it wasn't a new idea. Yet, they re-invented it in so many ways. Another example is, of course, Google, going against established search portals when they came about.
* There's an obviously good idea, people have tried it and "proved" that it cannot be done. Then somebody ignorant of this fact goes ahead and does it anyway. A famous example of this is Spencer Silver of 3M inventing the adhesive for the Post-It notes. He is quoted to say "If I had thought about it, I wouldn't have done the experiment. The literature was full of examples that said you can't do this."
* There's a good idea, others have implemented it with modest success. Then somebody comes along and blows it out of the water. Best example I can think of for this is the iPod. MP3 players were common before Apple, so it wasn't a new idea. Yet, they re-invented it in so many ways. Another example is, of course, Google, going against established search portals when they came about.