Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
It's capacitive touch, like your touch screen. It will only accept a button press if it's with something that works on a touch screen. My theory for this is that if they made it only be force sensitive, your pocket could set it off even if it didn't press just the button. They probably had to implement it this way to avoid any force on the bottom of the phone setting it off.
 
Tried some Head touchscreen running gloves at Costco today and they did not work.
 
It's a little disappointing that they didn't think about usability when removing the physical button.
 
Because it's capacitive. There is no physical button anymore so it's all software driven. It's the same reason you can't use your phone's screen with most gloves. It requires the small electrical signals produced by your body to recognize a touch or press.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.