If automated vending machines are the remaining hope for NFC, that's pretty weak.
A geofenced app -- if not Square, then Apple Passbook or others -- could prompt me on my own device's screen: "The vending machine here requests $1.50 to dispense your Snickers. Press 'pay $1.50' or 'cancel'."
The soft-interface device screen is much more flexible than the NFC-tap/wave-in-the-right-place gesture. Your own device screen will be better for doing things like:
• pre-authorizing a purchase before buying a tank of gas
• requesting an emailed receipt
• offering immediate feedback (or adding a tip)
• avoiding possible confusion/chargebacks about amounts paid.
That could mean 'app-style' payments have not just usability benefits, but also cost and legal benefits over 'NFC-style'.