I've had that fear every once and while, but the sites that I post on don't let people copy-paste anything that people write, and I don't think anyone wants to take the time to type something I've written word-for-word, so I'm not too worried. I post things on figment, it's a great site to get feedback from other writers on your work, and no one can copy-paste stories that are posted. You should check it out!