They marketed their service for years as 'free from chargebacks' and then (without notice!) silently deleted transactions which had, in fact, been charged back: http://venturebeat.com/2012/03/07/tradehill-sues-suing-dwoll...
Harassed as many people as I could for information on FiSync so I could try to offer integration to local credit unions and banks and couldn't get any real information out of them on it; it was a phantom program back when I was looking.
How would Dwolla help Square cut out the CC companies?
Credit cards won't be immediately replaced as they are accepted virtually everywhere. I think Square could be positioned well to replace credit cards though using the old Microsoft model of embrace, extend, extinguish.
Embrace credit cards in the short game. Extend with direct payments (bank to bank and alternative line of revolving credit). Extinguish; pull the plug on the credit card companies once they achieve high enough rate of adoption.