Obtaining a copyright release for your photos is very important. Copyright offers you the possession of your images to assist in preventing their misuse or any use by any means without your authorization. Nobody wants to make great work and have it taken from them. You deserve to be paid well for the photographs you make, and the authority believes so too. That is why your photographs are automatically copyrighted the moment you press the shutter release button on your camera.
They are protected under the Berne convention, which was implemented in 1988 (at least in America). If you all of a sudden see your photographs appearing in magazines or online without your consent, you have the full right to sue the specific person or establishment for copyright infringement.