Mammoth has signs encouraging a 15' buffer. Now, that may be for MOVING skiers/boarders as opposed to stationary, but I try and give at least that much even if it means slowing or even stopping to make it happen. I certainly don't want someone within a ski length of me if I'm moving or standing still. I assume others feel the same and try and offer them the courtesy of not coming too close. Until I can read their mind I try and err on the side of being overly cautious. Who knows which way they'll move (or not move). There are no turn signals in skiing and even if there were most people wouldn't use them!
And yet...how close did that snowboarder get to me on Wednesday?