Theft isn't usually an issue unless you have worked really hard on an image or site and you don't want people claiming your hard work for their own. Theft isn'y really a big deal, but I have been around some who really get upset over it. There are a few things that you can do to stop "basic users" from stealing your ideas or images. You can create an image watermark. A watermark is a text string or a image that brands an image as belonging to your site. You can also use a right click device. A right click device stops a person from being able to right click on your website. If they can't right click, they cant save your image. There are ways around right click devices, but they will deter the average Joe. I discourage right click scripts and such, but I do use watermarks here and there.
A No Right Click device is available for download under the Java Tips and Tricks Section.
This is a growing discussion and I will update it as I see fit.