[davepeck]

Having worked with a few sites that offer both direct-entry and PayPal payment options, I'd say PayPal gets far less than 10% of the transactions.

Given that PayPal has more established accounts than Checkout or AMZN, my assumption is that those services would get even less.

I understand business' distaste for co-branded UI; it can be a jarring experience for users and it often feels unprofessional.