Allows copyrite holders to recover lost earnings though law suits. Increase sells of legal material. Some of the freedom of the internet is removed. Also, with millions of users online, it will be very difficult to police the internet. Sell MP3's at a reduced price.
Copyrite holder gets some of the money they are owed.
Also very hard to police this. There is no right answer to this. I agree that the copyrite holder in intitled to the money from the sell of their products. I also agree that not giving the holder their money is the same as stealing it from them. However, I also believe that the trade of information and ideas is the key idea of the internet.