Originally Posted by Skeat
And, I do hope that you keep a running list of people that did not follow the exchange for future exchanges. If the swappee is not in good standing, they should not participate in the future. I've been in many exchanges, swaps in the years and this is normal to keep a no-no list. Life can happen, but, there are ways to not let someone else down.
Skeat makes a good point. It has happened in other swaps I've been involved in, too.