Whiting Petroleum just experienced a 'fat-finger' as we are sure Pisani and his ilk will describe it. What clearly happened was the headline/story scraping algos were tripped up by a sentence containing a bullish start and a bearish finish...
Whiting Petroleum Corp. explored selling itself [BULLISH buy buy buy] earlier this year but decided not to proceed after buyers balked over the oil producer’s asking price [BEARISH sell sell sell], according to people familiar with the sale efforts.
By the time the algos had read that first sentence of a WSJ Deal Journal blog [3] post, the stock had pumped-and-dumped over 8% in 250 milliseconds - at which point humans entered the party (and sold). Efficient liquidity providers indeed.
[4]
and in more detail - the action took place in 250 milliseconds as the sentence was read by all those liquidity-providing algorithms...
[5]
(h/t Nanex [6])