Sorry to be blunt, but is this a post of some clueless person trying to blame IB for providing a great feature? Normally, best would be last price traded. Now, try trading MINI CURRENCY FUTURES and you will realize that a stop triggered by bid / ask can be of value. I swish my broker would offer that - I program a logic for that now. Why? Because while bid/ask there reflect forex rates, sometimes trades are rare. Tade triggerd stops would be triggered.... sometimes 20 pips through the stop. There one needs bid/ask triggered stops. But seriously, this is a great feature of IB. Using it right, though, is your responsibility.