The courier we use for international shipping is DPD. When shipping to Norway they request your 11 digit birth number for customs/tax purposes. We will contact you prior to dispatching your goods to request this number. Please be assured that we do not pass this number on to any other third parties and it is not kept on file or recorded anywhere.
Details of this number can be found here http://en.wikipedia.org/wiki/National_identification_number#Norway
Necessity of personal identification number for Norway document (DPD) can be found here Necessity of personal identification number for Norway