i have never been involved in a trade that someone wanted to bust, or a trade at a price that was "clearly erroneous." but i would suggest the simple mantra of "do unto others as you would have them do unto you." if you mistype a price and get filled instantly, and it costs you thousands of dollars, would your attitude really be "oh well, cest la vie! better be more careful next time!" do the other guy a favor and agree to break the trade.. if there was a software glitch and the confirm was erroneous or something, cut the guy some slack and break it, rather than "finders, keepers!! neener neener neener!" on the other hand if there is a 30 min rule i feel its more legitimate to not agree to break it, because you have a responsibility to look at your own confirms for crying out loud!