>>What I'm really looking for is some form of officialgovernment communication on the subject (unless of course the hosts are the ones who are manning the passport control desks at the airport).
So call the nearest Korean consulate/embassy. Answering this kind of question is part of their job.
I actually already had put a call in to them; the relevant person was out of the office, but I left a message. We'll see what they say.
--Ken
This is from travel.state.gov
KOREA, REPUBLIC OF (South Korea) - *Passport and onward/return ticket required. A visa is not required for a tourist stay of up to 30 days. For longer stays and other types of travel, obtain a visa in advance, $45 fee. AIDS test required for persons working as entertainers and staying longer than 90 days; U.S. tests results accepted. For further information, check with the Consular Section of the Embassy of the Republic of Korea, 2320 Massachusetts Ave., NW, Washington, DC 20008 (202/939-5663 or 60) or nearest Consulate General: CA (213/385-9300 and 415/921-2251/3), GA (404/522-1611/3), Guam (671/472-6488), HI (808/595-6109), IL (312/822-9485), MA (617/348-3660), NY (212/752-1700), TX (713/961-0186) or WA (206/441-1011/4). Internet: www.koreaembassyusa.org