Why is Apple offering an unlocked iPhone 4?

What prompted Apple to start selling unlocked iPhones? The best answer may be the simplest: A new iPhone is on the way, probably in September. There are three long months between now and September – long months where Apple could see interest in the outgoing iPhone 4 start to fade. By stirring up a minor press flurry around an unlocked iPhone, Apple can keep general iPhone buzz high, gin up a few sales, and generally hold off against incursions from Team Android for as long as possible. Then again, maybe we're a little conspiratorially-minded these days. What we do know is this: The iPhone 5 is almost definitely on the way.