I've experienced a lot of chargebacks, unfortunately. For some reason some gang of people from Vietnam keeps using my site to verify stolen credit cards work. Originally this all happened through a third-party service which I had no control over (I couldn't preemptively block suspicious transactions). I switched to Swipe and eventually saw the same fraudulent transactions coming through (one was 50 charges with the same card with a minute of each other).

Sick of it all I finally got minFraud setup and working with Braintree as the payment processor. So now, I use Braintree to authorize the card, then do a fraud check through minFraud. If the fraud level is low enough, I submit the payment for settlement, otherwise I void it.

Since putting minFraud in place I haven't had any chargebacks.