Using backups as an archive probably isn't feasible anymore because we now have to access the data more frequently due to the regulatory and discovery requirements that are happening. However, we believe that backup and archiving are two separate processes that require two different tools. You wouldn't use a hammer to put a screw in and vice-versa. Backup software is a great way to move data and create a copy of it in case there's a corruption or deletion. Archive software is a great way to move data into a separate environment, index it and make it searchable as well as readily retrievable.
Backup and archive software can coexist and actually complement each other. For example, if you archive messages out of a primary environment, you can then back up that primary environment much quicker because there's less data to copy. In addition, if you have an archive and it contains evidence, business records as well as key older messages from employees, you want to make sure you protect that archive. Adding that archive to the backup scheme is a requirement. So, there are some overlaps to how you can use backup software and archive software, but they should be used for the right things. Archive before you back up and then back up the archive. They must coexist; one shouldn't replace the other. They should complement.
Go back to the beginning of the Email Archiving in 2008 FAQ Guide.