The same thing could happen with people, someone finds an old story but doesn't realise it's old, tells a few people, starts a rumour and then traders sell off stock. At least with an automated system you can improve the algorithms.
Yup - like the occasional trader that misses a decimal point and sends a stock whirling off in the wrong direction (most trading systems have mechanism to prevent this, but it still crops up now and then).
Whilst this is an unusual case - 99.99% of the time the access and currency of information available today actually makes for a much improved market.
