Mixers, Remixers and the like.

When an artist creates music it is their own. They have taken a series of sounds and arranged them in such a way that they find meaningful. In principle this is an idea that most of us can agree with. But then what happens when we introduce the idea of the remixer or the mixer into the world. These are people who take parts of already established music and combine them in a new fashion to produce a song.
I believe that these men and women are in their own rights artists. And just like artists they have varying degrees to the quality of their music. There is a large percentage of these mixers who do very little to change a song, in this case I say that they are still artists. However, they are artists that I feel don't produce very good art.

Do you believe that there is a certain point at which a song becomes a new song? If so is it possible to located this point?