Who Owns Your Pictures?

In class the other day we looked at some interesting stories related to copyright issues in terms of photography. For example, a young girl named Alison Chang had a picture of her taken and uploaded to Flickr. This photo then became an advertising campaign for Virgin Mobile, without the consent of Alison or her parents. The case addresses the interesting debate over who owns the rights to pictures that are posted to the internet for public viewing. I believe that pictures with no copyright are fair game if they are significantly manipulated. If they are not changed in any way, they should not be available for commercial use without the consent of whoever posted them.