Copyright is a clumsy tool. When one copyrights a work, one reserves all rights to that work, rights which are interpreted in the US (and other) courts in increasingly strict ways.
But sometimes one wants to waive certain rights in certain circumstances. What then? That's where Creative Commons steps in:
"Too often the debate over creative control tends to the extremes. At one pole is a vision of total control a world in which every last use of a work is regulated and in which 'all rights reserved' (and then some) is the norm. At the other end is a vision of anarchy a world in which creators enjoy a wide range of freedom but are left vulnerable to exploitation. Balance, compromise, and moderation once the driving forces of a copyright system that valued innovation and protection equally have become endangered species.
"Creative Commons is working to revive them. We use private rights to create public goods: creative works set free for certain uses. Like the free software and open-source movements, our ends are cooperative and community-minded, but our means are voluntary and libertarian. We work to offer creators a best-of-both-worlds way to protect their works while encouraging certain uses of them to declare 'some rights reserved.'"
If you want your ideas protected from economic exploitation, yet available to a wide variety of people, CC is your best bet. There's even a short film explaining what it is and how to use it.