http://www.cnbc.com/id/49333454A single mysterious computer...

http://www.cnbc.com/id/49333454

A single mysterious computer program that placed orders — and then subsequently canceled them — made up 4 percent of all quote traffic in the U.S. stock market last week, according to the top tracker of high-frequency trading activity. The motive of the algorithm is still unclear.

The program placed orders in 25-millisecond bursts involving about 500 stocks, according to Nanex, a market data firm. The algorithm never executed a single trade, and it abruptly ended at about 10:30 a.m. ET Friday.

[Speculation is that it was an algo designed to slow the market down in specific stocks to gain an advantage and these were tests to calibrate it. Liquidity my @$$. If it isn't stopped one day all h@ll will break loose.]