djIn what seems more like an idle hack than a serious product, NASDAQ has set up an automated account that responds to requests for specific stock prices via Twitter. NASDAQ’s account, named @datajunkies, will respond to a Twitter direct message that contains a ticker symbol, in the format $GOOG, with a response such as, “$GOOG: 452.16 +2.06%,” somewhere between five and twenty seconds later.

NASDAQ’s service is cute, but shouldn’t be mistaken for a serious trader’s tool. You can only get the price of one stock at a time. Moreover, the service plays on the current perception of Twitter as a “real-time” tool. Computer engineers know there’s no such thing as a real-time response in the sense of being instantaneous. Information traveling through a computer can’t exceed the speed of light, which takes about one-seventh of a second to travel from one side of the world to the other. Data read or written from a hard drive or stored on another server takes more time to retrieve.

Most of all, tweeting through Twitter’s servers is not an instantaneous act. Try it yourself sometime by tweeting between two accounts on the same screen. You’ll see that it can regularly take 30 seconds for a new tweet or direct message to appear on its destination screen.

In the time it takes for NASDAQ to auto-tweet your stock price back to you, the servers belonging to Wall Street’s high-speed traders have already spooked the market with bluff orders to goose the stock’s price, canceled those orders, and bought or sold a few hundredths of a second later. Your real-time info is, sadly, totally stale.