Its upsetting but not TOO upsetting. In our league rules, if someone accepts a trade, but posts a message on the message board within 20 minutes of accepting the trade that he has cold feet, he has a right to have the trade negated. Its to prevent people from making stupid snap decisions. The only condition is that the trade negation cannot occur on sunday (oh such and such had a good day, so I wont trade him now) or because of an injury (oh, now that Leftwhich is definately out for the season I dont want him anymore).
So if that happened to the commish, I'd be angry, but I'd get over it. He handled it pretty well.