EAs trade with zero emotion. This can be good, but if the market turns against the strategy the
EA uses, almost all of them will continue to try to trade as if the market was still behaving the way they were optimized for.
Spend some time watching some movies on the SciFi channel about robots turning on their masters and attacking them due to some tiny flaw in programming. There are a lot of stories in the reviews area telling of good EAs that suddenly went bad and killed account balances.
Does this mean you should give up on the whole EA concept? Maybe, but maybe not. An EA that uses a reasonable stoploss, good risk/reward ratios, and that
stops trading after several losses in a row or if drawdown exceeds a predefined limit would be reasonably safe to take for a test drive on a live account after a few weeks of successful demo testing.