They say that ideas are a dime a dozen, but I would say that some ideas are definitely worth much more than others. Ultimately, before you invest any real effort in a new idea, it's also worth thinking about whether you have time to do so, and how this would affect the other projects you're working on, and the people you're working with. There's been many times where someone pointed me to an existing project that was an absolutely terrible implemenation of an idea similar to mine and basically told me that because this project had failed to take off, the idea would obviously not work.