it's unclear to me whether you need a merchant account to use square; i'm assuming from "0-$60 in under 10 seconds" that you don't.
if you don't need a merchant account, the market for this is massive. there are millions of people who provide services and sell products who take cash, check, or paypal only. many of these people are dying to take credit cards with zero hassle, which square lets them do.
I thought about that too. Someone has to have a merchant account, so it's possible all of the payments go through Square and they act as a clearing house where they redirect payment to the correct merchant. I could see that leaving them vulnerable to chargebacks. I wonder what kind of rates they're offering to users.
if you don't need a merchant account, the market for this is massive. there are millions of people who provide services and sell products who take cash, check, or paypal only. many of these people are dying to take credit cards with zero hassle, which square lets them do.