There are also other methods available that will let them backup offsite locally. Backup Assist+Rsync is one useful way. SFTP is another.

There are 3 Main Backups You want:
1. Onsite - External Hard Drive/NAS
2. Offsite Local (SFTP/Rsync) - Home or some other office
3. Offsite (out of state/country) - Carbonite/Mozy/iBackup