The marketplace is not a static environment. It evolves with every trend, every product introduced, every government regulation passed. An idea that works today may not -- in fact, probably will not -- work tomorrow.
Unless the idea is one that can evolve.
Krispy Kreme is famous for its doughnuts, which used to stand as symbols of warmth, deliciousness, sensuality, love. Then Atkins struck. People changed their worldview and started regarding doughnuts as carbs, which mean calories, which mean fat.
KK is no longer that popular, and they are losing money, all because the idea (The Doughnut) could not evolve. Sure, perhaps the product could -- they started offering whole wheat doughnuts last year, with less calories and more fiber. But it will still induce the same feelings of guilt on people, because it's still a doughnut.
A while ago my friend Dave ran an idea by me. I don't want to give it away here; without going into too much detail, it had to do with various types of cards people carry with them every day: ID cards, credit cards, discount cards, etc. I thought the idea in and of itself had merit.
However, it suffers from a fundamental problem: how is it going to work when, in the future, we stop using cards altogether? When we start using RFID tags for identification, biometrics for authentication, and our cellphones to communicate with ATMs?
It is not an idea that can evolve, and thus will be short-lived even if its successful.