Two Countries Separated by What Again?

Readers who follow politics probably heard about the minor gift exchange kerfuffle betwixt British PM Gordon Brown and Barack Obama.  Now, as some feared, Brown has discovered he can't view his gift of 25 American movie classics because the DVDs are encoded only to play in North America. Readers who follow me probably recognized this regional encoding as another form of price discrimination, as it allows firms to charge different prices for the same product by separating markets geographically.