I got my N900 from Vodafone UK on contract and it is not locked. And it is paid via contract, not bought separately. (i.e. I did not pay the full price of the phone, only 30£ or so at the beginning)
Thanks for the info. Haven't talked with Vodafone for a while because their data prices always seemed high. T-Mobile and O2 were cheaper, hence me knowing a bit more about them.