I haven't used the Backup User feature, but from the brief line or two that I've read it appears to be a free online storage solution of some description for users to keep personal files on DH storage that might be against the TOS to keep on your website account.
In essence I understand it's for uploading your personal (not for public eyes) files for the purposes of portability, etc. rather than backing up or keeping a copy of entire existing online accounts that are publicly accessible via your sites.
To offer a solution we'll need to know what you're actually trying to accomplish
Maximum Cash Discount on any plan with MAXCASH