When that lost iPhone appeared on Gizmodo, many people were skeptical. It did look like an iPhone, or a knock-off of an iPhone. The idea was even floated around that this was merely an unfinished case, a tester, holding the guts of the upcoming device.
Certainly it looked different. There were black seams disrupting what had previously been a (mostly) smooth case. It seemed almost contrary to Apple's design aesthetic.
As of the WWDC yesterday we now know what the lines are for, they and the steel band are part of the iPhone's antenna system. One side dedicated to Bluetooth, WiFi, and GPS; the other larger half to UMTS and GSM.
Hopefully this means fewer dropped calls, and dare we hope, better 3G reception. Steve intimated as much last week.
Steve's discussion of the antennas starts at 2:45 in the video above.