Something you should be doing anyway, but here's another good reason to carry ID with you.
From the Korea Times:
The Korea Immigration Service's crackdown on illegal immigrants this year has been met with controversy due to allegations its officers are making random checks on those who look like foreign workers.
Members of the legally residing foreign community are also upset at the failure to stick to a legal set of procedures.
"Immigration officials make raids on the street," said a foreign scholar in Seoul who spoke on condition of anonymity.
She said three Nepalese foreigners were grabbed on their way to get a haircut recently, while a pregnant woman was taken outside of the city last week. Others are caught during routine shopping errands, she said.