One concern I’ve had with flat out blocking movement is the feeling the player will get. During some tests of mine with a Rift DK2, if I lock the camera position and do not move it as the player does, I get extreme nauseousness near instantaneously. I don’t have my Vive yet so I’m not quite sure how this feels in a walking room-scale environment, but I suspect there may be issues if you are walking and suddenly your camera stops.
I think overall the better idea for VR would be to black out/fade out the camera when an occlusion with an impassible object is detected with some kind of light fog indicating which way back to the correct play space.