A difficulty for creative persons on the Internet is that they want their art/content to be widely distributed (go viral) but still want attribution. Traditional copyright law makes such distribution difficult since each person copying the such content would need to explicit permission of the owners.
A non-profit organization has started a web site called Creative Commons that provides the owners of copyright protected work (art, photos, articles, blogs, etc) with standard licenses that allow dissemination of the material on the Internet without the loss of attribution.
Owners of copyrights can select how much of their material can be used - with and without attribution. The owner can also select whether or not derivative works can be created from their work.
I recommend it to bloggers and anyone who would like their work to be re-distributed on the Internet.
Of course, if you did not want your work to be redistributed, then these licenses would not be appropriate.