Locavores advocate paying attention to the distance your food traveled before it reached your table.  They want you to be aware of the social cost of the the tomatoes you buy.  Steven Landsburg ridicules this kind of micro-mindedness as follows:

You should. You should care about all those costs. And here are some other things you should care about: How many grapes were sacrificed by growing that California tomato in a place where there might have been a vineyard? How many morning commutes are increased, and by how much, because that New York greenhouse displaces a conveniently located housing development? What useful tasks could those California workers perform if they weren’t busy growing tomatoes? What about the New York workers? What alternative uses were there for the fertilizers and the farming equipment — or better yet, the resources that went into producing those fertilizers and farming equipment — in each location?

And he helpfully points out that accounting for all of this is unnecessary because these costs are already all summarized by the price of the tomato.

But even if markets are perfectly competitive, the marginal social cost of a tomato equals the price plus the under-priced cost of the environmental damage from the fuels used in transportation.  Any given locavore has his own private belief about the size of that gap.  So a locavore wants to know how much energy was used in order to calculate the total gap.  And locavore advocates are doing precisely the right thing by presenting that information.

On the other hand, this guy, the guy who Landsburg was actually ridiculing, is spot on when he points out they often present distorted information.