What's crazy is it only takes one bad actor to cause problems like this. Often fraudsters will just use one website to "test" if a card is good, by using it to make a small purchase. If it goes through, the card is good. One fraudster might do this 100 times on a small site. The merchant is liable for the chargebacks that will come within 30 days, and each chargeback typically costs $15. Additionally, if the percent of chargebacks as a total of all transactions goes over 2%, the merchant account provider will likely close the account due to risk.