When the iPad was first introduce in January 2010, one of the neat things was that it included a mute switch, which was later switched to a rotation lock, which was then switched again in 4.2.1 to a mute switch. After plenty of backlash, iOS 4.3 was released, and a new option in the Settings app allowing for the switch behavior to be customized.
The new menu option allows you to switch not only the switch, but also the button on the multitask switcher. When the side switch is set to “lock rotation,” the button in the switcher is set to mute. And the opposite is true when the switch is set to mute.
The option is a great addition to the OS, it shows that Apple is looking to allow you to customize the OS more than it did previously, and that nothing is ever final in iOS.