In the building where I work, there's a large grocery store in the basement level—larger than the grocery in my apartment building. I often head down to this grocery to find something to supplement my lunch, and because I go down there so frequently, all the lady cashiers know me by sight (not that I, a hulking, doughy foreigner, am all that hard to miss). One lady has been in the habit of overdoing her greeting and service: whenever I appear at her register, she becomes exaggeratedly chirpy and cutesy—not in a flirtatious way, but in a more patronizing way, as if I were a retarded child whose every utterance in Korean is seen as a major accomplishment. She repeats everything I say, the way a mother might repeat her baby's first comprehensible words and phrases. If I say, "Please give me a ten-liter plastic bag," she responds, "Oh, a ten-liter plastic bag!"
The other day, she probably went too far with the high-voiced chirpiness. I know this because the cashiers on either side of her started cheerfully ribbing her: "Hey! Why're you acting that way with him? You're not usually like that!" She tried to make excuses for her own behavior: "Oh, well, he's a foreigner, and he speaks Korean so well..."* My own impression was that she put on the exaggerated show because my presence was actually freaking her out, and she didn't know how she was supposed to interact with me.
When I swung by the grocery this morning for some victuals, Mrs. Smiley was the only person "womaning" a cash register, so I lumbered up to her, expecting more of the usual cutesy treatment. But she surprised me: today, she was professional and businesslike—not an iota of cute to be found. I think the ribbing she'd received from her "sisters" had gotten to her, and she now has a better idea of how to interact with me. It's funny to see that this happened, but also a bit sad: in East Asia, where difference isn't valued as highly as conformity, there's a proverb: "the nail that stands out gets hammered down." While it's true that I prefer that the cashiers simply treat me as they would any other customer, I also feel a bit sorry for Mrs. Smiley, who has been brought back into line.
*I don't actually speak Korean "so well," but it seems ingrained in Korean culture to coo over foreigners who manage to put together a few words in Korean. Any utterance at all is seen as passing over the threshold of linguistic expectations. I've heard various explanations for why this is so: Koreans believe that their language is too difficult for non-Koreans to learn (a fact routinely contradicted by the increasing number of Korean-fluent foreigners on TV); there's a sort of ambient sadae-jueui (사대주의—roughly, a kind of reflexive obsequiousness) that impels Koreans to feel obliged to speak in English around foreigners; etc.
ADDENDUM: let's talk a bit more about the implications of sadae-jueui. First, I should note that I find the concept offensive, but if Twitter is anything to judge by, the concept pops up, not just among expats who live in Korea, but also among Koreans who are fluent in English and who have experience living abroad and/or interacting with foreigners. I gather it's a real thing, but as an explanation for Korean Behavior X or Y, it makes me squirm.
I also think that, if there are indeed any traces of sadae-jueui in modern Korean society, those traces are disappearing. The other side of the story I told above is that most of the cashiers treat me the way they treat normal people. Mrs. Smiley was the only one acting differently. I'd like to think that sadae-jueui is a real problem in North Korea, where kowtowing is a matter of survival: you can't afford to sass back at the local authorities (although I have seen video of this happening), for whom insufficient submissiveness can mean punishment not only for you, but for your whole family.
I also think the idea of South Korean sadae-jueui is contradicted by how Koreans on the street generally act in crowded situations. They honestly don't give a shit whether there are foreigners present when it comes time to push onto a bus or into a subway; there's a pervasive, equal-opportunity rudeness that is, in a sense, a sign of egalitarianism: I don't care who you are—you're in my way. I've also never sensed any over-obsequiousness from taxi drivers, bus drivers, restaurant workers, bank tellers, coworkers at the office, fellow teachers at the uni, or anywhere else, really. So I think that the explanation for Koreans' strange politeness when it comes to their linguistic expectations has nothing to do with sadae-jueui.
I do think that Koreans have low expectations when it comes to foreigners' linguistic performance, and part of this may be because of foreigners themselves, especially our military guys, quite a few of whom aren't in country long enough to gain a real grasp of the language before being rotated out. At the same time, I confess to being frustrated that Koreans aren't reacting more visibly to the ever-mounting evidence that many foreigners these days actually do attain a better-than-basic level of competence in Korean. The time for low expectations has passed and, as I've written before regarding assimilationist attitudes, Koreans have every right to expect that foreigners should speak some level of Korean after having been in country for several years, just as we Americans expect expats in the States to be able to speak English if they've been in America for more than a few years.