This low weight is partially because of size and partially because Sony is using Lithium - Ion batteries which are smaller and lighter than traditional battery bricks like Anton Bauer, for instance. The Sony literature states that the fully charged BP-L90 battery will last approximately four hours and fifty minutes recording time. No more changing tapes during the long-winded CEO speech, or having to ask for a recess during a video taped deposition session. With a shoulder mount camera, weight and balance play a large part in how easy the camera is to use. If a camera doesn't rest well on your shoulder you're not as likely to be relaxed, and you wont get as steady a shot as you will if the camera is balanced and feels like a part of your body.
Most cameras have a stiff foam shoulder pad.
The complaint with these pads is that shoulders come in different sizes, but usually, shoulder pads do not. Sony has addressed this with a new style of shoulder pad that is amazing. It conforms to thin and to thick shoulders, making this camera very comfortable. This larger and heavier lens gives the camera a noticeable front heaviness. If the wireless receiver were on the back end, or if it had a traditional brick battery, the weight balance might equal out.