Agreed - this functionality, as a system administrator, is very important.
Atlassian needs to keep in mind that its customers might have to follow strict Government guidelines on data retention, and this should also be taken into account when providing a backup solution. Right now, the backup facility just doesn't 'cut the mustard'!
The restrictions applied to backup frequency could also be an issue - 48 hours per backup and retention time of backups on WebDav is only 24 hours, Why?
Ideally, it would be great if Atlassian provided the backup functionality as a service. ie. You just set your preferred backup period, and Atlassian will store your backups for you (on WebDAV).
Obviously there will be a limit of the number of backups, ie. Atlassian will only retain the last 24 backups. Customers can find the best period that suits them (they may want to be able to restore as far back as 2 years, so they choose a monthly backup, other customers may want to be able to granularly restore on a set day so the trade-off is they can only go back as far as 24 days).
Another option is to keep allowing customers to download backups from WebDAV so they can have the 'granular' restore option but also keep historical backups dating past the 24 day limit by downloading from WebDAV every 20 days (or so).
This feature request was originally opened for Cloud (on-demand)