Back when I was a linguistics student, I learned the word "isogloss". Simply put, this is the name for a geographic boundary based on word usage. You either live in a place where it is called "pop", "soda", or "coke".
Just want to point out that Obama can't win without the olive green states.
Sociolinguistics is a mildly interesting field of study, the fodder for third hour bar discussion on a Tuesday night. On any given night at Dave's, Mr. Ryan will mock my northern cities vowel shift and I give him shit for saying "every so once in a while". This gives me amusement because native Californians don't think they have an accent.
I remember Elfini's practice wedding. When I met her in the lobby after the ceremony, my first question was "so who is this "Don" that Wes married?" And there is such a look on the face of these native Cal's when you try to get them to enunciate the "awww" sound. I'm sure their instinct is to think that I must be hearing it wrong. Then again, they are a people who never learned to cover their mouths when they yawn.
Back to the soda pop thing. There is a perfectly good reason that we in the midwest call it "pop": we call everyone by their last name. Soda's last name is Pop. There.
Go in Peace