Crediting. As far as I know PayPal Mass Payments requires the recipient to have a PayPal account (in fact, we do use Mass Payments for customers who choose to be paid by PayPal). Crediting via ACH, on the other hand, merely requires routing and bank account numbers - which is something everyone has! The whole point, which neither PayPal nor Dwolla solve, is to use the existing financial network, not create a new means of money exchange.

I'm interested in chatting in more detail with you about this. Would you drop me an email if you would like to discuss further? My contact details are in my profile.