No matter how good or professional your host or backup service is if they make a mistake you are stuffed. They can offer as many money back guarantees as they want but it won't get your data back.
Today all users of Journalspace.com, a hosted blogging platform, woke up to discover that all their data has been lost, the backup is useless and if they don't have their own backup they will have to start from scratch.
Repeat after me