Since nobody answered, I will give it a shot.
Post# of 56323
I am not sure your question if framed correctly in part. What I mean is that they don' t really hide or make background sales in reality. They are the market maker. Which means that they buy lots and try to sell lots. Well say a lot is a unit of shares. They make money between the ask and the bid. So, they can combine, or slice up lots to suit the purpose of making money. What you see really, is that sometimes they will try to fool you into thinking the bid is going up to get you to buy, or, that the ask is going down to get you to sell. They do this by the blocks they show you. So, in essence, along with looking at L2's you should pay attention to volume, and short term charts to see what they are REALLY doing. Below is a link that explains some of this better than I can, in part, and is using the higher exchanges for examples. Note, manipulation is much easier on the pinks as I am sure you know. I hope this helps.
GLTA
Note: If I am off on this anyone please correct.
http://www.investopedia.com/articles/financia...tricks.asp