Except that part of PayPal's business model is saying that you can depend on that callback. This isn't on the business here, it's on PayPal. Now, I'd agree if

Except that part of PayPal's business model is saying that you can depend on that callback. This isn't on the business here, it's on PayPal. Now, I'd agree if you said that PayPal isn't suitable for a business to use, it should be relegated to the realm of individuals and small businesses who don't know better, but that's different than what you seem to be saying.