The real question is not what can be backed up. The real question is, what can be recovered. If you take a system backup once a day, then you can only ever recover up to the point of that backup. Or can you. Have the system administrator demonstrate a restore (obviously, do this test on a test/dev system, not production). If that works, great. Now, ask the business, can we lose an entire day's worth of data? If not, then you also need to do log backups or differentials... but, there's the problem, those won't work with your system backup. So, assuming your business is like most of the businesses I've worked with, you're going to need to do a regular, SQL Server, backup and then logs/differentials to allow for the ability to recover to a point in time short of once a day.