United has since said that it will honor tickets of those who have already flown but will be canceling the tickets of those who have not. However, the Department of Transportation is currently investigating the matter and may be able to overturn United's decision since there's a federal rule that does not allow ticket prices to increase after they've been booked.
There are two opposing views on this issue. On one hand, some think it's unethical to take advantage of "error" fares, while others think that companies need to be responsible for their mistakes. What's your take?