And North Korean refugees are not the only ones threatened.
The Foreign Correspondents' Club of China has a whole page on protecting sources and examples of what could happen if those sources are not protected. While this page is specific to issues in China, the issues it raises and the guidelines it suggests are true for any repressive government in the world.
A discussion of this kind fits in nicely with the SPJ Code of Ethics:
And in the cases under discussion here, that "harm and discomfort" could mean torture and death.