Often you'll see trades of a single share where the brokerage...

Often you'll see trades of a single share where the brokerage costs more than the stock. The computer is sussing out prices, forcing you to pay more - or get less if you're selling - than what your online broker's screen says.

Talk about unfair or, in finance speak, an uneven playing field. No wonder the corporate watchdog, the Australian Securities and Investments Commission (ASIC), is having doubts, except, like everybody else, it isn't too sure exactly what the computers are up to.

They can run rampant with a faulty algorithm until somebody pulls the plug, but not before the market has been shaken and confidence drained from it.

Either they're undercutting a seller or overbidding a buyer to get in first, beating you to the punch even at your price.

Worse still is flooding the market with fake bids, suggesting something's happening and there's momentum, only to cancel them a nanosecond before the market opens. Once, that was considered market manipulation.