In "Growing the business" Paul Hawken says that if people tell you that something is a great idea then it is to late. It means that it already exists that is why the people who think its a great idea could recognize it in the first place.

So if people tell you that's nuts or that you are too late or that it would never work, then you might be on to something. In that case you don't need to worry about any one copying it as it will be absolutely unique to you.