Yes this is a common play for locals. They usually are fading the market (from what im told). So like with today market was selling off hard and there was a big bidder who was willing to step up and bid 5k contracts near the lows. The locals seen this and made their bids one tick infront of him (the thinking is that if my bid gets hit the market surely won't have enough steam to take out all 5k contracts) So anyway they all got hit and then the bid flips to the offer and since that big bid is what the locals were banking their trade on they puked their longs.