Quick, answer the following question:
When you ask someone you're eating with in a restaurant what they're having, this is
a) out of idle curiosity
b) in order to avoid the embarrassment of ordering the same thing
I would answer b), and until a few months ago I would have thought of this as common sense. Apparently, though, it isn't. What brought about this realization was a recent incident in a restaurant with a group of people who all decided to order the same thing. Someone at the table said to me, "Hey, Positive, I bet you're dying of embarrassment right now." Which I was. Everyone wondered both how she knew, and why I would be embarrassed, while I wondered why they had no manners. You see, the person who knew I was embarrassed was a fellow Chicagoan, and was equally embarrassed, but had previously realized that this was a little-known instance of regionalism. I was skeptical, but some casual asking around has basically confirmed this, that Chicagoans find it embarrassing to order the same thing as someone else at a restaurant, whereas no one else cares.
My interest in American dialects stems from a general interest in regionalism and cultural diversity. I have a theory that is too vague to be testable (the best kind) that accounts for why people assume that American culture is becoming homogenized, while linguists are observing dialect divergence. My theory is that localisms are being subsumed by broader regionalims, which are diverging. The fact that I could have a strong cultural taboo, one that I had never heard articulated, moreover, that the people I was eating with (among them my wife) were ignorant of shows that such cultural differences are at least plausible. If this were really to conform to my theory, then this taboo must be more widespread than just Chicago. Have you encountered this taboo? Do you yourself have it? Is it the craziest thing you've ever heard of?
What strikes me is that even though most non-Chicagoans I've asked don't know about this taboo, everyone is familiar with the phenomenon of asking, "What are you having?"