There is a sticky thread on this forum about why to NOT publish your essay here and most of the reasons have to do with others stealing your ideas or even your essay. But even if no one does that, there is an even more important reason: Plagiarism Checkers are often used, especially now with electronic submissions. And the plagiarism checker will find YOUR OWN ESSAY online and mark your submission as plagiarized.
I took one of the essays recently published in this forum of CC and ran it through a common plagiarism checker The result that came back: "WE HAVE DETECTED SIGNIFICANT PLAGIARISM IN THIS TEXT." We don't use real names here, so when a college gets back a report that an essay is plagiarized, there's no way they can tell that you were the original author, even if they try to follow up, which they might not have the time or inclination to do. You're majorly screwed by your own essay!