I don't pretend to know the mechanism by which they are...

I don't pretend to know the mechanism by which they are manipulated, possibly bots. What I do know from watching these trades for many years is that you cannot trust what is in those stacks. They may look genuine, but if they are automatically shuffled to the end of the queue or removed completely on a whim, then they are not, in my mind, genuine. Many times I have watched a share for hours waiting for the right time to sell, during which time not a single trade has occurred. As soon as I make my trade, there is a flurry of activity and the share price is back to where it started. Have you ever wondered how it is that we can have 20M shares traded in a day and the share price ends up the same. If you want to see a share that has a genuine stack in buy and sell take a look at DDR. They have very few floating shares and it is very difficult in that situation to do much manipulating.