http://www.thefab.net/topics/social_general/sg05_adult_sites.htm
"The adult web site operators collected $188 million from 1997 to 1999, some of which may have been obtained fraudulently. The credit card billings allegedly generated "tens of thousands" of complaints.
Owners of scores of adult Web sites have been charged with billing thousands of Web users for supposedly free services, and billing other consumers who have never visited the Web sites at all, the Federal Trade Commission announced.
"We've examined the digital adult content industry for a year and determined that there was an unacceptably high incidence of disputes about transactions," said American Express spokeswoman Joanne Fisher. American Express will no longer cover credit card transactions from porn sites.
VisaUSA says this is one of the top two or three complaints that they've ever had, and that they have thrown porn sites out of the VisaUSA system. "This is probably the biggest Internet scam I've ever seen," says Steve Baker, director of the Federal Trade Commission's Midwest region."