I agree about paypal being convenient, but it's also true a lot of frauds can happen through this system. I agree, some of them are the user's fault for not conforming to instructions or clicking links in unsolicited e-mails or such. Still that leaves a large amount of them which might have been prevented if paypal enforced tighter security and had some sort of chargeback protection.
Indeed, you can learn a lot from visiting Paypalsucks, I know I did.