A couple of years a Windchill PDMLink site had someone come in and setup their system including vaulting but without ever backing up the vault. They recently ran out of space on the vault drive and in the process of expanding the drive capacity, something happened and they lost several years worth of vault data ....without a backup. They are trying to recover the tens of thousands of missing files from the local desktops of the users, I'm not sure how that's going to work out. This reminds me of another story at a Windchill large site with very experienced administrators that lost a computer room to floods. There was a problem with the LDAP backup and portion of the LDAP tree was missing and needed to be rebuilt manually by the administrators. I think it took a couple of days.
In both cases the stress levels of the administrators would be through the roof. Ensuring the safety of the data is a core job of administrator; in at least one case I'm aware of I believe data loss was cause for dismissal of the administrator. I'll be honest there once was a time, when I wondered if backups were necessary, no longer, over the years I've seen enough disasters and near disasters (no you cannot delete the .dbf files from the Oracle load point because they are taking up a lot space!) to know things do go wrong, and without backups things may not turn out well.