Anyone else out there noticing this more frequently lately? I'm not talking the usual odd order of a few hundred thousand shares or a few million shares, I'm talking about large orders of heavy size on the pay-big-fees-to-remove exchanges in the depth of book, usually on the NBBO.
It's probably not someone who's trying to buy/sell large size... since no one moves large size upfront without trying to hide it a bit. Sounds more like someone trying to do the very illegal and very risky tactic of spoofing the market... post a huge buy order so that your smaller sell orders get filled faster at better prices... Do you have any more details?... how big the size is in relation to the rest of the stock... does the side show up on one side and then show up on the other side after the stock has moved or a few moments later... does it vanish when trades start printing against it?
Usually 10x the average book size, quotes don't stay for more than a second, if even that. Seems to happen in liquid stocks quite a bit lately.