Currently our foreman-rake db:dump and db:import_dump tasks read and write to the root of wherever foreman is installed. (https://github.com/theforeman/theforeman.org/pull/245)
Users by default don't have access to /usr/share/foreman on a regular install made via foreman-installer.

A 'destination' argument that defaults to ~ would ensure users get a backup at a location they can write to.