My college roommate was from Hawaii, so he stayed with my family for the Christmas holiday. His mother shipped a crate of citrus from Hawaii, meaning I learned for the first time how grapefruit should taste. Locavores are right: fresh fruit direct to the table are the best.
Regardless, I've regularly had grapefruit halves for breakfast over the last 50 years. Why? Grapefruit from the Safeway taste good enough; they satisfice even if they aren't the platonic ideal of grapefruit. And that's the crack in the locavore armor. Many people develop a taste for tropical and subtropical fruit: your citrus, bananas, etc. which most Americans cannot grow locally but which we learned to value. That simple fact breaks the connection between place and product, so we're willing to accept the idea of fruits and vegetables being transported to the store from further and further away. (See the history of United Fruit for how far back this goes.)
The economists would tell us it's a balance of the utility of the produce, mostly the taste, and the cost and they'd predict, rightly, that the ability to put good-enough tasting produce on the shelves of the supermarket only increases with time.
My proof: some of the best blueberries I've tasted in a good while just came from the Safeway, grown in Chile.