I came across a post from Author Nathan Bransford that made me think. You can read it here http://blog.nathanbransford.com/2012/06/why-writers-shouldnt-be-paranoid-about.html With all the things writers have to worry about should posting your query online be one of them? No way. No how. One of the best things to come out of this series of tubes we call the internet is the support that communities bring to their members. Like it or not as a writer you are a member of a community. Use it, participate in it. You can only benefit from it.
Another thought, and this ties into the many questions I have seen asked about copyrighting work before showing it to other writers, is something I had to learn the hard way. Very few ideas are that truly unique. Also until your idea sells 50,000 copies it probably isn’t a good one. (I am being positive by adding the, “probably,” in that last sentence. In truth no ideas are good without the sales to show for it.) As Mr. Bransford says in the post, “The success of your book will hinge on the quality of its execution, not on the originality of the idea.” Truer words have never been spoken.
So worry about how you are going to finish the last half of the chapter your started this morning. Or worry about whether or not you can sell a protagonist who is an introverted sex addict. Worry about the fact that your main character has two different spellings for their last name but for the love of the universe do not worry about someone stealing your idea. I am reminded of a vulgar truism that equates opinions to a certain body part that plays a role in the digestive track. As writers we all have more ideas than we can make stories of, all without having to steal each others. Don’t let fear of someone stealing your story idea keep you from participating in the writers’ community.