The USB CCK does support some audio. the site at the end says:
Audio: As Macworld contributor Glenn Fleishman first reported, standard USB-audio accessories--namely, USB headphones, headsets, and speakers--can be used with the iPad via the Camera Connection Kit's USB adapter. When you plug one of these audio accessories into the adapter's USB port, all audio is routed through the USB-audio accessory. If you're using a USB headset, the headset's microphone also works for audio-recording apps, as well as audio-chat apps such as Skype.
While I didn't have enough USB headphones, headsets, and speakers on hand to test this feature exhaustively, my results with a handful of devices confirm Glenn's experiences. In fact, the iPad treats a connected USB-audio accessory much like a set of headphones connected to the iPad's headphone jack: If you unplug the USB cable or adapter while music is playing via the iPod app, playback pauses. On the other hand, I did occasionally experience some odd echo-like distortion when using a USB headset.
Site:
http://www.pcworld.com/article/195013/ipadcamera_connection_kit_connects_other_thingstoo.html