You know, I agree with a lot of the posters about how teacup is a marketing ploy, teapot, isn't. but I think it is more than that.
Its almost like, on a rap record, an artist can drop the "n word" and no one gets all offended, because a) he is a member of that group, b) he usually isn't using it to cause offense or be a slur and c) its use is not seen as negative within that subsection of the community.
key is C, by the way.
Here at YT, we all are so conscious of the teacup being a misleading term, used by unscrupulous breeders trying to get more money & potentially doing harm to the breed by intentionally breeding overly small dogs. Whereas we can say "teapot", in that rap star way, cause they are OUR dogs, we love them madly and no one is trying to make a big trend out of it.
So....that's my 4 cents (cause I have a teapot and 2cents aren't enough!!)