1) Most Americans use credit cards because they need the credit. That is something that won't be solved. Many of us also like the benefit of rewards (miles, dollars, whatever). To get payers on board, you need credit, rewards, and exclusivity (i.e. is this the only payment method available at somewhere where I want to shop). The last 2 meaningful companies were paypal and discover card. PayPal had millions of Ebay sellers using PayPal AND they initially paid people to become members. Discover card started the cashback movement and was the only electronic payment option at Sears (largest retailer in the world at the time).
2) Due to the Durbin amendment (which went into effect October 1st of this year), debit card cost to a FeeFighters merchant for the average transaction in the US is about $0.25. (http://feefighters.com/durbin). They now cost 22 cents plus 0.05% of the transaction. The reason that I mentioned a FeeFighters merchant is that most processors do NOT pass through the savings to the customer, you only get that with interchange-plus billing (which only about 10% of merchants are on, mostly big merchants).
3) Doing some quick math, that $350 million in transaction volume gets them to $175,000 in revenue per year ($350M/$500 transaction size)*$0.25 = $175,000.
Still, they have a fantastic opportunity and I for one am rooting for them. Ben has the same roots as FeeFighters (had another company, was pissed off at how much he was paying in processing fees). He chose to tackle it a different way, one that is probably harder to execute on but can make more change in the long-run. Having met him, I bet that he didn't quite say the words in that headline.