回複：fair use就是說朋友之間拷貝dvd自用是合法的？

No. Even though it may be argued as fair use, there is another federal law on point, the DMCA, digital millenium copyright act. It basically says you cannot copy a commercial DVD for personal use, not even on your own computer. It is somehow in conflict with the spirit of fair use but as far as I know there is no court ruled otherwise so as for now DMCA still controls.