This isn't necessarily a good idea.

If you share it with someone that has the resources to build it faster than you, it's just going to create headaches for you in the future.

So, it's a good idea to share the generic idea, but not the specifics.

One of the businesses I'm running now (which is profitable) spawned from an idea I saw on a message board about 6 months ago. I knew the original implementation of the idea would never work and I improved on it. It's a direct competitor to the original person that posted it.