Is that wall actually being eaten, or did he pull 1k of it?
He's pulling, very frequently. It looks scripted, everytime the buy orders get close is when it just disappears for a second. It reappears when the bids get sold into and the action is lower.
It's probably bitstamp's automatic ordering system. Instead of market order or putting a price, "simple" ordering puts and moves the wall for you to the closest price in the opposite side every few minutes.