Previous discussion on the seller side: https://news.ycombinator.com/item?id=1726552

A cruicial problem of running marketplaces is any pathway by which stolen CC numbers (readily available by the dozen for pennies) can be turned into cash will be heavily targeted by fraud. See discusson on this here: https://news.ycombinator.com/item?id=5091069 ,and esp the recommendation on getting a Fraud Guy.