Cardpool.com Cardpool Stole $350 in gift cards from me, Internet

Cardpool is an online company that buys and sells preowned gift cards.   I had $350 in unused Best Buy gift cards that I wanted to sell.   I agreed to sell the cards for $323.40 and was emailed a prepaid shipping label. They offer a choice to receive a higher value for your cards if you take the credit in an Amazon Gift Card.   I chose this option. I followed their instructions and sent them the cards on Aug 11, 2012 (transaction 1392622).  

Cardpool claims they never received the cards.   According to Best Buy the cards were cashed 4 days after I sent them.   I would chalk this up to bad luck and the cards just getting lost in the mail, but upon further research about this company I have found many similar complaints.   I suspect they have an internal theft problem within their company.

I requested that they honor the exchange they had agreed to do.  They were unwilling to do so.  My concern is that they have a history of doing this to customers.