Proof is in the pudding, as they say. Before Apple's iPad, there was no lack of companies making tablets, they were made, they were pushed, they were shown around and hyped. Nothing came of them. To the dump, all of them.
iPad was shown, just 3 years ago. It was cool, it did stuff, it was touch like the iPhone but better in many ways. Where everyone before had failed, Apple succeeded. Why? Because Apple created a product that worked, and on many levels.
Now, everyone and his mother are coming out with tablets, which they claim don't copy Apple. Horse hockey! If Apple merely created a market for tablets, then their competitors should just offer their old junk and see how that flies. Bet they wouldn't sell, and they couldn't give them away.
No, Apple's competitors stole the essence of the iPad -- they had to to compete. The iPad is the emergent result of many technical parts, many of which existed before, but were tweaked by Apple engineers and combined in ways others had failed to see.
Yes, Apple's competitors all had the hydrogen and oxygen, but it was Apple who made the water.