Mobile payments have been around in Africa for years, mainly because there's no legacy systems to compete with, and the lack of a solid banking/payment processing industry has made growth occur unopposed.

Whereas the incumbent players in North America (most credit card and payment processing juggernauts) will most likely put up more of a fight against systems like Square.

There's a recent podcast about the mobile payment industry (http://www.cbc.ca/spark/2011/02/spark-139-february-27-march-...), check out the part about Mobile money in Kenya, and the Smartphone wallet.