Payments is an especially interesting example to take in emerging markets. The delta between developed and emerging is often especially huge in payments and banking.

I was part of the founding team of a mobile payments startup SnapScan (http://www.snapscan.co.za/) in South Africa. We had to flip the "US" models around completely. Informal merchants often had no bank accounts and only feature phones, but many consumers had credit cards and smartphones.

We ended up giving QR stickers to merchants, notifying of payment success via SMS and depositing payments in an "instant" bank account that they could withdraw cash from ATMs without a card (just their feature phone).

Looking at how people pay in the US, I would think that our approach wouldn't have made any sense to someone who hadn't seen South Africa (or a similar country) first hand.