in reply to
How many continents have you visited?
I'm not sure I can say I've visited North America, as I live here (assert $continents = 1) but I have gone to Europe ($continents++) and some Caribbean islands (are they part of North or South America or neither?)
I'm not sure that "continent" is a well-defined entity. How about a poll asking how many tectonic plates we've visited?
Information about American English usage here and here. Floating point issues? Please read this before posting. — emc