I would give them 24 hours to make payment(or deposit if the item requires inspection), move on to the next person. Their lost!!.
I once made a trade with some schmuck on this board, asked a buddy of mine to take a RBTA (thats what the other party wanted in trade) out of his tank, took it to the frag swap in Brooklyn and waited 3 hours for the guy which never showed. I lost faith in MR members ability to come thru on their commitment and will not no longer hold things for people I don't know personally. Too many dibbers on this site that don't live up to what they post.:bablefish