Starting from Fusion 7, VMware support Virtual USB camera. This allows the physical camera (USB or built-in PCIe FaceTime HD) to be shared by both the host and the virtual machine at the same time. This feature works for most of the USB cameras.
The virtual USB camera will try to open a stream on the host camera and render the video stream to the guest. By default, virtual machine uses virtual camera, and the pass-through of USB camera is blocked.