It's always tough to justify additional costs, right up until the disaster occurs.

Fortunately most large companies can perform off-site backups these days via their intranet, and smaller companies can utilize one of the many online storage companies for off-site backups.

OTOH, when disaster on the scale of the Japanese Tsunami strikes, and the entire city is leveled, it's going to be a while before most of the IT departments recover, unless they are ready/willing/able to relocate immediately to a suitable unaffected location.