[pentae]

It actually runs deeper - the reason 'probability of fraud is higher' may as well be called 'probability of buyers remorse' is higher. In the industry we call it friendly fraud. When a customer finishes what he came to finish doing, the regret of spending 50 bucks can often result in a call to the bank. Some credit card providers make it even easier you can just click 'dispute' online and pretend like it was fraud to get a refund.

Interestingly, 3D Secure (verified by visa etc) was created to solve the issue of friendly fraud, but whats mystifying is it applies for all categories except for Adult.

Of course, this isn't the whole story, there's other factors like aggressive affiliate marketers - but it's a big part of it.