Could be worse... I've said I was keen for something being sold locally, organised a time to go and pick it up.. had my wife drive 30 minutes to pick me up from the office so I could make it there in time (one car family).. drive another 15 minutes to their house to be there at the arranged time.. only to have them call me when I am literally around the corner (still 10 minutes before pre-arranged time) and say someone else has bought it when they came to look at some other stuff.
There was much rage. Had wife & kids not been in the car with me it is likely I still would have completed the drive to ensure this person clearly understood my thoughts about their conduct.
More on topic... I bought a few things from the trading section on here before I made my first post, pretty sure a google search for an item is actually how I found the site in the first place. Even now I don't think I have trading access. I don't think you can "regulate out" dickhead sellers on a forum like this without causing the moderator team a whole heap of extra headache (having been a moderator on another community forum, there is nothing worse than the he said/she said over a trade that hasn't gone to plan), but it is definitely poor form IMO for sellers to not at least offer an explanation like "Hey, sorry mate.. You got in first but I've had a heap of trouble free transactions with this other guy and owe him a favour or two so I'm going to let it go to him" or "Sorry, I got a couple of other PMs before yours.. will let you know if they fall through"