Your point is well made narmac....its a hypothetical situation, and unless someone tries it we will never know.  They could dump using iceberg orders so as not to advertise their intent.  Or they could start slamming the bid, in which case they'd know soon enough if there were any iceberg orders on the bid side to provide support.  

White swan, black swan.....there's a bird lurking somewhere.  Now watch them announce something big only to have the market reaction be...."meh".