Happens all the time Minerva, have a read of a few of my TLS telstra posts, about the appearing and disappearing 1.2 million share orders several times a day. Funnily enough, once you have a bet at the TAB, you cant cancel a bet after 2 two minutes unless it's a genuine error, even for a $1 bet, and once you place a bet at the casino you cant ask for a new hand if your cards are duds, or after the croupier calls "no more bets" but on our ASX casino, you can cancel a $5 million order once it's objective has been fulfilled, as in a seller puts on a buy prop, and a buyer puts on a sell prop...oldest trick in the book. Large orders over a certain amount maybe 100 grand in value, should not be able to be altered unless there is a price sensitive announcement that follows, for the rest of that trading day.
