is the headphone jack. Compared to other headphone jacks, this one is designed for small portable devices, itself being light and slim. Furthermore, with the weight distributed on the bottom, it works to plant the plug into the headphone jack, and when you're walking around with the ipod, all cord movement is absorbed by the sheath running up from the plug.
Now, on other plug designs, most notably the L-shaped designs, cord weight and movement actually move the plug around, thus potentially wearing out the headphone jacks much more quickly.
And on straight-up headphone jacks, which stand 2 cm up, often the cord is subjected to so much bending that it severs (i've had this happen to me with the sennheiser px200 cord)
Now, on other plug designs, most notably the L-shaped designs, cord weight and movement actually move the plug around, thus potentially wearing out the headphone jacks much more quickly.
And on straight-up headphone jacks, which stand 2 cm up, often the cord is subjected to so much bending that it severs (i've had this happen to me with the sennheiser px200 cord)
