Yes; in order to qualify as a skeuomorph it doesn't need to _not_ serve a purpose, it just needs to retain design cues that were essential to the function of the original but not to the function of the copy. The iOS camera could very well do its job of taking pictures without making a shutter sound. The shutter sound is an auditory cue for the user, but not a side effect of the camera's function.

As another example, consider the iOS notes app[1] before the iOS6 design transition. The app looked like a legal pad---complete with a leather binding across the top and remnants of pages torn off. These were essential functional characteristics of the original object, but were retained in the copy only to provide visual cues to the user that remind her that the app she is using is just like a notepad.

[1] http://cdn.redmondpie.com/wp-content/uploads/2012/02/Notes-2...