One of the nonprofits I helped suffered something similar. Tens of $10 charges, most of which were disputed, refunded, and charged a chargebacked feed pretty much erased all funds raised within the month. I trusted Stripe more, but now I believe they are no different thatn Authorize.net, maybe even a bit worse. Anybody can be got on any website using Stripe and test a credit card. A chargeback has a different meaning and that's why it's penalized and I believe Stripe are abusing the system and wrongly charging merchants a chargeback fee. In our case, we're using the most popular WordPress donation plugin - it's not like we've coded this ourselves or that our system was breached - somebody just went to a donation form and tested stolen credit cards with $10 - that's all! And we have to pay $15 for each of those attempts, which Stripe didn't stop! How is this exactly our fault?!