1) “People only use 10% of their brain’s capacity.”
Wrong. A goofy idea instigated by third-rate (in critical thinking terms, even though in some respects cutting edge technically speaking) turn-of-the-century research. They opened some folks’s skulls, zapped different places with an electrode, and asked the subject what happened. 90% of the zaps resulted in no perceived reaction. They concluded, with the Ancient Egyptians, that this gray matter must therefore be used as mere filler. So lame!
[Addendum: apparently the source of the myth is not certain, but the fact of the myth is. See Snopes article.]
2) “The average piece of food in America travels 1,500 miles from farm to plate.”
Possibly true, but consistently quoted out of context. The study that this is based on was done for food consumed in (or near, I forget) Chicago. Not for the country as a whole. It is possible that Chicago provides an accurate approximation of the national average, but there’s no good reason to expect this to be true. I wouldn’t be surprised if the real number is significantly lower, or (more likely, to my gut instinct) quite a bit higher. Plus, the study was done a few years ago. International trade in food has only increased. Grapes from South Africa. Bell peppers from Israel. Them’s far away places.
[Addendum: I've just done some quick Googling, cuz I wanted to see if I could find the source of the food mileage estimate. Turns out that there's more than one source (shocking!) since a few different people have studied it over the years, but none that I saw was very recent. So anyway, this is a question that deserves a good, up-to-date, and thorough study. Any graduate students out there in search of a topic?]