http://crofsblogs.typepad.com/english/2005/02/fish_or_fishes.html

Canadian usage permits "beer" as a plural; American usage, as far as I know, does not.

Linguists call the line between two such usages an "isogloss" (literally, "same language"). Just as an isobar on a weather map describes a region of equal air pressure, an isogloss describes a region where most people follow a particular usage or pronunciation. In the "beer" example, the isogloss runs right along the US-Canadian boundary.

Similarly, isoglosses separate British "lorry" and North American "truck," and Californian "fender bender" and Tennessee "car smash" ....

I suspect isoglosses also exist between social classes and generations. My generation uses "said" for "said." My students use "like":

"So Crawford is like, 'We have a quiz on Monday,' and I'm like, 'Omigod, I can't be there!"