Instead of:

>     if first_name.blank? && last_name.blank?
>       'Name: unknown'
>     else
>       first_name + ' ' + last_name
>     end

One who prefers one-liners could do:

    "#{first_name} #{last_name}".strip.empty? ? "Name: unknown" : "#{first_name} #{last_name}"

Furthermore, it's better to move such code to a helper method or a decorator using https://github.com/drapergem/draper