I do not think that there is much that can be done to protect the intellectual property rights of the people who create pictures, videos, and music. Many video and music sharing sites have been shut down due to their sharing of video and audio files; however, when one site shuts down, another simply starts up. With that being said, I think that we must all take it upon ourselves to get others to realize that someone else put a lot of hard work and effort into these projects. However, if someone is selling the intellectual property of another person for profit, this could be classified as fraud and would then involve police action and lawsuits. As long as people are only using the intellectual property of others for their own enjoyment and not claiming it to be their own work, I do not see much of a problem with it.
I think that it is acceptable to copy sounds or images for use in your own work when you cite the work. This shows that you did not in fact create the pictures, videos, or music. It also shows that you are giving credit to the person or people who actually did create it. Scanners, video digitizers, and audio digitizers are all tools which are there to help us share our work with others. As long as people give credit to the original composer I do not see why there should be a problem with using these files which have been put out there for the world to see and hear.