How much would it cost you to recover your data if you lost it?
If your tapes are offsite can you get to them when you need them?
How much will it cost you for each minute your data is inaccessible?
Won't you sleep better knowing your files are mirrored offsite at a secure location yet accessible 24x7?
A March 2004 Gartner report determined that "online server backup services cost less and deliver more".