If I publish and disclosure my idea to the public, what assures me that others won't see it and take advantage of it?

The usual mechanisms of intellectual property protection, such as brand registration and patents, can also be applied in projects that are looking for funding via the crowd.

Nevertheless, everyone has ideas and, most probably, someone already came up with “this one" before. What is relevant is how the idea gets implemented.
That's where the team, know-how, networking, etc., are important.

What we suggest is that the project author discloses just enough to attract backers (by showing credibility and implementation capabilities) and not so much that other competitors can copy it.
Most projects looking for funding do not include detailed technical plans in the description, but just enough for the supporters to judge and decide to contribute.

The idea will have to be made public at some point. With the right team and financing secured, all that is left is to implement faster than the others.

To sum up, we think there are more advantages in publishing a project to test the market than to keep it secret in order to avoid being copied.