The argument is that on some unspecified future date when Amazon has a monopoly, they can arbitrarily choose to hold payments for more than a day and screw up a

The argument is that on some unspecified future date when Amazon has a monopoly, they can arbitrarily choose to hold payments for more than a day and screw up a business' cash flow and cause them major headaches. Anyone who relies on PayPal today already accepts the risk of having their account/funds frozen, and there are already many horror stories of businesses having tens or hundreds of thousands of dollars locked up for a three-month investigation (only to go bankrupt in the interim).