There are level(s) of information available beyond Level ll. I'm not sure if there's a Level lV, but there is certainly a Level lll. For the appropriate monthly fee, you can obtain not only the bids and asks and the houses and all of that, but also you can see all the stop loss orders. They're sitting there, visible, plain as day. So if the bid level falls off to a certain extent, those stop losses might prove to be worth going after with a lightning strike of market sales. By driving the bid down, the stop losses are automaticially triggered. All the perpetrator is thinking about is his average price, taking into account the costs of driving the bid down, and the prizes obtained at the stop-loss transaction price.
In summary, it's a strategy to obtain a large block of shares at below market prices, because the market usually returns quickly to a point near where it had been before the stop loss raid began.
Stop loss orders are excellent for protecting you in a falling market, and are part of some people's exit strategy. But the risk is that they are visible to people willing to pay the steep fee per month to view those orders in real time, and they may be triggered when the market has not actually been falling.
Lar
