"A marketable idea doesn't have to be a big, groundbreaking idea; it just has to provide a solution to a problem or be useful enough that other people are willing to pay for it. Don't think innovation; think usefulness."That's from The $100 Startup by Chris Guillebeau.
I think we throw away our ideas because we feel they are not "big" enough and simply don't have the wow factor that we think good ideas should have. But it's getting started, actually doing something about even a simple idea that is difficult and the step that almost all of us don't take. The idea you have is probably not original and many others have likely come up with the same thought, but acting on your idea will make you a rarity.