Automation technology is not available to the masses. I work on meta models, and we have automated the systems development lifecycle long time ago, still in use today. Limiting the need for programmers. Banks, industry and governments are still running the code we developed in the 80s. The same have been done with animated movies. Tools have been developed to limit the amount of drawings.
you do not want a situation where you bring up screen and say sell 100 shares of microsoft and the shares disappear before you sell 100. this would imply a) as happened to bill ackmann there was a mole in the organisation possibly with a 5g telephne who held ackman in very high esteem or b) somone was racing down west highway, across to kansas and then buying and sellingboth of these situations would be worth investigating. one solution is put a large coil in ackmans telephone so what he sees is not what the market is seeing from the persepctive of someone indide the market.
the last thing i would say on the subject of automation. the reponsibility of an exchange is to fairly price trades. the exchange cannot price as fast as the fastest coiled telephones if there are moles. to put it simply if connecting both fast and slow participants an exchange should be computerized.
No matter how fairly the exchange prices the trade. The bid and ask determines the price. If i get filled using limit price, i'm a happy camper.
sometimes i go to trade on exchange a and price different from exchange b. a gentleman trades both to lock in a 100th of a bid offer. stat arb. he doesnt close and has friends in margin. imagggine
we all need margin facilities like stat arb. trust me. they do a lot of trades, bigger than the biggest swaps desk in notional for example. now its a lot more serious than you think. there are contracts which according to many do not offset all the time.
let me tell you an etn is a debt security and an etf is an equity. so if french bank blows up the investor in the etn would lose his principle. its not old an im a fan but not riskless or particularly helpful. they have massive positions, are expensive to run and need to do a lot at that yield. margin trading.