I think, but could be convinced otherwise, that the bursts of small parcel algo trading are related to the dynamics of the volume profile on the day not so much about some sort of mainipulative behaviour.
However after a lot of observation I do believe it can have a profound but not obvious effect on price action under certain conditions. I am not sure if this is deliberate or just an unintended consequece. Essentially this happens when centrepoint selling is used in conjunction with the privileged order stream access that is in common useage by brokers.
An example would be someone firing off a buy order at say 80 cents when the spread is 79.5/80 cents. The order is intercepted by the broker who sells into it at 79.75 cents. the buyer is happy and gets a discount. However the seller on top of the sell queue is denied the order and is stuck there. So this gets repeated systematically and the outcome is that the buy queue gets decremented but the sell queue is stuck as the buy orders are being filled from a dark pool i.e. a hidden buyer.
Eventually the only way for the seller to sell is to drop the price or otherwise just sit there hoping the problem goes away while meantime the buyers are being mopped up. I have seen this process used extensively on some emerging stocks over long periods and every time I see centrepoint selling kick in now it makes me very nervous.
