To Random42's point, simply having an idea like: "Wouldn't it be cool if cars could fly" is obviously worthless.
I think that I was not clear enough:
I think of an idea as a vetted plan. An idea, based on an understanding of a problem and a market, a vision on how it will make money. A design a spec and even mock-ups.
Far more than a simple statement of wishful thinking.
For me, whenever I have "an idea" I take it as far as I can take it sans having it developed.
For example, I have a current "idea" in the medical space (which is where my current full time focus is) that is a patient entertainment system.
This idea is based on several years of full time health care systems design experience designing two hospitals each with a budget of more than $500 million. It is an iterative evolution of a previous idea which we implemented and built and released open source, and a solid understanding of the market, the challenges and the sales cycle. Further, it is arrived at with the inclusion of hospital IT and Clinical staff that I have worked with on two projects -- and input from the founder of one of the existing market leading companies in this space.
I have a product spec, financial model, business plan and mock-ups.
This is my "idea" -- it is not worthless because it is a proven, fully informed documented product plan.
I still need development and a host of other things to accomplish this.
I have millions of simple wishful thinking ideas as well, but for anything that has value - real potential I go through the above.
I apparently was not clear with what I thought an idea was... I hope this makes my perspective a little more clear.