Boy Genius Report has a story of an iPhone 4 that was returned to an AT&T store for "incendiary" reasons.
In other words, the damn thing caught on fire.
According to the customer, the flame-out occurred when the i4 was plugged into their computer using the (Apple-supplied) USB cable. Initial examination suggested that the phone's USB port was defective (no, duh…), generating enough heat to not only melt the port AND the cord, but also heat the antenna bezel enough to burn the customer's hand.
Let's just hope this is an isolated brushfire (pun intended), and not another design flaw to be added to the i4's Wall of Shame.