I can see what you are saying about creating mixes. If you buy music, why shouldn't you be allowed to use it in a different way? I guess the real question is are you depriving the artist from making money. so if you do a remix for yourself, should that be considered OK as long as you don't sell it to someone else or give it to someone who will not buy the original artist's music. The Grey album you mentioned is aptly named. I think it is a "Grey" area in the copyright law.
I am overwhelmed by the topic of copyright. We are living in a world where creativity is valuable and should be protected. We are also living in a world where people will cheat and steal others creativity and claim it as their own. In a world where plagiarism is as common as a Starbucks drink on college campuses, laws are being put into place to try to protect those individuals that have worked hard to get their ideas declared as their own.
The videos Good Copy/Bady Copy really got me thinking. Sampling is a music style that I enjoy. I even use samplings of music when I make movies for my classroom or for my own personal uses. Does that mean that I need to go through court proceedings to give those artists their due? No! I pay for that song that I sample with my own money. I remember when “The Grey Album” came out and all the controversy that surrounded it. I was surprised to find out that the artist never made any money off of his “art project.” For his creativity, he deserved SOMETHING. I may be naïve, but creativity should be rewarded and protected.