The key idea here that most entrepreneurs miss is that you really need to vet your own ideas. Many aspiring entrepreneurs dream up an idea, and then stick to it doggedly, either because its the only idea they have, or they find it technically interesting. They don't want to discover that it won't work, so they don't try to figure it out! This is a bit like writing some code, and then not testing it because you really don't want to discover that its buggy.