How does this affect traders trading their own money? http://www.nytimes.com/2009/07/24/business/24trading.html?src=twt&twt=nytimes
How does it affect them? These 'bots are scamming $billions from other trader/investors & mutual funds due to manipulation and "colocating" at exchanges. They're all in bed to screw everybody else. Look at intraday charts & you can see how this market has changed over the last 3-4 years. These scammers have totally changed the market.
1) It depends on your time horizon. 2) Longer-term traders/investors shouldn't care because it doesn't affect longer-term trends. 3) Shorter-term oriented traders should be concerned because they'll tend to be "last to arrive at the buffett table" if they're using slower order entry to the market. 4 If there are too many robots/algos in the market, they'll eventually cannibalize one another and shake out the weaklings.