If an artist wants to get their message/masterpiece etc. out ito the public domain so that people can listen to/see it, then once someone else see it they can do whatever the want with it so long as they don't claim it as their own. There would be a big difference between music/web content and physical paints, sculptures, etc. Of course with the latter category those are only someone else's propert once they pay for it. But I'm guessing that the question was aimed more at web content, and specifically, music/movies on the internet. People can take that content from the internet with ease but it isn't their property. Creative content is the maker's alone until he displays it for others. Once that happens, the maker deserves all credit for the content in its current form but someone else should be allowed to take it and change it substantially enough so that it is their own. In concrete terms, that would be difficult to define except on a case by case basis. But once you display your content, be wary that others may want to use your ideas for their own benefit. And unless you have a patent on your idea, you have no say in what they do with your content.