Doesn't seem to me like it's specific to Android. Facebook implemented the same thing in Android, iOS and mobile website almost simultaneously, and many iOS app

Doesn't seem to me like it's specific to Android. Facebook implemented the same thing in Android, iOS and mobile website almost simultaneously, and many iOS apps followed suit as well, eg. Sparrow, Path, Steam. Also, a small gripe: with the Facebook iOS app, dragging the top-left menu button with your finger actually caused the side menu to follow exactly where you finger was, following the principle of Direct Manipulation (http://en.wikipedia.org/wiki/Direct_manipulation_interface http://en.wikipedia.org/wiki/Direct_manipulation_interface). The Facebook app on Android and mobile web fail to do this, as with the many other apps mimiccing this UI.