What's disruptive about Dwolla? PayPal has always let you fund payments by bank transfer and person-to-person payments are free to send and receive. As far as I can tell reading their site, they are PayPal without 90% of the features but a better mobile app, and the only benefit for merchants is the introductory $0.25 pricing. If ACH-funded person-to-person payments are going to disrupt the banking industry, why didn't it 12 years ago when PayPal started doing it?
In addition, Paypal is currently making $$$ on ACH payments that they charge their full fees for. They can flip a switch and change those back to free or $0.25 and kill any Dwolla advantages.