Work For Hire Agreements Prevent the Unexpected

"You should be greatly concerned about who owns the work you specially commission. For example, unless there is a special kind of agreement in place before any work begins, someone who contributes material to your new book or web site can, in theory, sell that same material elsewhere without your permission. Worse still, if there is no written agreement, and you want to adapt that material, or publish it elsewhere, you will probably need that person's permission.

Similarly, if you hire someone to illustrate one of your short stories, unless there is a written agreement that says otherwise, you may be surprised to learn that the illustrator has become your coauthor. These seemingly odd results follow from the fact that under copyright law, authors are presumed to own the copyright in the works they create. The best way to avoid these problems is by having a written agreement in place before any work begins."

Read more in this article by Attorney Lloyd J. Jassin.