In a business where "the hard technical problem" is how to stop fraud while allowing legitimate transactions to occur, you'd expect bad engineering to mean that the fraudsters win and the whole thing blows up. But what seems to have happened is that they've simply overcompensated on the other side. It's easy to stop fraud if you just flag everything as fraud. You end up with pissed off annoyed users, but you don't go bankrupt.
It's too bad. I really wish PayPal was a vibrant alternative to Visa & Mastercard; they fundamentally have the trust model right. It's just that they've been failing at execution for decades now and even with the braintree acquisition it looks like they're dead in the water, milking the last of their fading reputation.
Stripe is really the class act here, but they're playing a very conservative game. I wish they "owned" the payment process more instead of just being a front for credit cards. Maybe someday.