Nilofer Merchant in her HBR article Let Your Ideas Go makes case for sharing the ideas rather than holding on to them.
When you have an idea, you make a choice whether to hold it close to your heart or to share it with few people who can help you take it further or evaluate it or share it in open space for anyone to look at it, take it, use it, modify it, critique it and thrash it.
Most ideas held close to one person may remain only with him. Practically speaking to make an idea a reality, you would need help from many people who would help you realize it. So the real choice is between sharing it with select few with a confidentiality clause between you or to share it publicly with anyone.
Traditional business sense would say one must keep an idea under wraps till it is ready to be released with a big bang, or till it has proven itself. Primary motive being protecting the idea from potential copying by competition or a fear that they might actually come up with something better than us with the same idea. You want to reap the benefits of the idea that you assume was born in your head, or at least emerged first in your head. You want to protect it using various laws available.
Think of a scenario where you let your idea be available to anyone like the ‘Ideas to Explore’ on this website and see them bloom in some other gardens. In the age of social media, you can leverage the wisdom of crowds to fine tune your idea, to get more ideas surrounding your ideas, to get a critical appraisal of the idea or find partners to work with on it. If you are someone who gets lots of ideas, you may not have the bandwidth to work on all your ideas but may still want to see them happen. Sharing your ideas, you may help you find the perfect pot for your ideas to grow.