It is a common misconception to believe that "backup" copies are legal, regardless if they're for personal use or not. Until a decision is made by the federal courts, the "fair use" law currently states that backup copies are legit as long as they are not put to use until the original copy fails or is destroyed.
However, part of the Digital Millenium Copyright Act states that circumventing the protection mechanism (such as Macrovision) is illegal. Therefore, the only acceptable option is to make an exact copy using a raw feed during the copy process, in which the resulting backup must remain in storage. Since most DVD's today exceed the petty 4.7GB DVD burners are capable of handling, exact backups are most certainly out of the question.
Just my 2¢