The fad this year among backup software vendors and changer manufacturers is to push centralized backup schemes. Most of these centralized backup schemes depend heavily on incremental backups to work, and an incremental set is less reliable than a series of fulls. Difficulty of full server restoration. For example, a lightning strike kills four servers, one of which is the tape server. If the backups were decentralized, all four servers could be restored simultaneously.
Redundancy is also very important.
Tape drives and servers are mechanical objects, and, as such, have a finite lifetime. When designing a large backup scheme with many servers and tape drives, it is important to plan to have enough unused tape space to cover the failure of any backup component. Tape media security is another thing that many people forget. Backup tapes contain a complete image of a business' production data. A used backup tape should never be casually thrown away.