I tested the Webcam support for VideoTexture.
It works when I start the gameengine in embedded mode from the blender gui. When I start the Player in standalone mode (or from commandline via blenderplayer) the texture will become just black and no camera image is shown. Playback of a moviefiles or streams work in booth cases, embedded and standalone.
I've made a small test blendfile, the webcam is hardcoded to /dev/video0, 25fps, 320x240.
Blender: 2.64, 2.65
Graphic: NVIDIA Corporation GF106 [GeForce GTX 460M] (nvidia driver)