Oh, something like that happened to a teacher of mine years back in some African country, can't remember where. She is quite a large lady and I have always known her to dress fairly conservatively. Still someone offered cattle to own of her companions!
Apparently she was travelling with a friend who was skinny and they offered less for the thin one! You've got to laugh sometimes, but yes, I guess it makes sense to try to respect the local culture, although I'm a fairly liberal person and I would have trouble having to dress in black from head to toe in a hot country but then again, I tend to use destinations where the culture shock wouldn't be so great.