I've been using PayPal plus another payment provider to provide other payment options and I can say that I get almost no chargebacks with PayPal. I think I've had one in the past year. The other company, I get several chargebacks a month. Their fraud protections just aren't nearly as good as PayPal.

In fact, I often spot fraudulent charges very quickly and have to email my third part processor to refund or cancel the payments.

I was pointed to http://maxmind.com by another HN poster, which is an API that'll give you a probability of a charge being fraudulent so you can verify it before passing it to the payment provider. I'm going to test that out in combination with Stripe.

If I recall correctly there is a mention of this on Paypal's story in Founders at Work.