[eazy e]

OK, so I have been a member for a few years. I have only traded once or twice. I made a trade with a member who seems to have good feedback on 6-15. I sent my cards out the next morning on the 16th. He marked them as received on the 21st. And thats the last I have heard from them. Not responding to my PM's and has not updated the trade on his end. I have checked and they have logged in everyday since the trade yet they have not shipped and the part that has really got me worried is not returning my PM's asking when they would be able to ship.
My question is: Am I getting excited for no reason or should I be concerned? At what point should I assume the cards are not coming? What if any recourse do I have?
This is exactly why I have been reluctant to trade. I love the OPG,Organize and Forums but the trading has always felt sketchy to me and it seems it didn't take me long to get burned...