It's alwsys good to check reviews, and whether they havs been verified by anything. Sometimes the person has been a member for 5 minutes. Sellers usually flake for one of two reasons, something legit goes wrong, or they recieve a better offer and decide to take it, too low to tell you.
Buyers seem to have a lot of family emergencies that also result in their magical disappearance from the face of the earth. The ones who are legit will try to explain and reschedule, apollogetically, stuff does happen.