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The second cable likely goes to a "wall wart" plug in transformer so the dock can supply charging power if the computer is off or if there is no computer. Or, possibly the charger uses more power then a USB cable can supply. I forgot the maximum current the USB standard allows but it's not a lot.
500mA. But that should be sufficient for the iPhone, considering that I can charge my current smartphone over USB if I choose (though it takes about two hours longer than the wall plug). If the iPhone battery is of higher capacity than is typical of smartphones (and it would seem to be, given the battery life stated), then it probably is for AC power as you suggest.
 
Being Smart.

Gizmodo is just trying to be smart again, just like they did when they said the iPhone would definately be released on Monday. I think the dock is for Cisco's iPhone. They should have know better than to take that name, I hope Apple runs them out of business.
 
someone should make a web site showing percentage of accuracy for all the rumor sites individually.... would be pretty interesting!
 
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