With over 400 million active credit card accounts on file, Apple had a prime opportunity to convert its customers using a sleek mobile payment system tied to the iPhone.

FORBES: Apple Unveils Faster, Thinner iPhone 5 With 4-Inch Retina Display, LTE Support (Live Blog)

Merchants that use Square Register are much more active than merchants who use the Square Card Reader: Register users are five times more active every week than those who use the Card Reader and they process about two times more revenue.

FORBES: Move up http://i.forbesimg.com t Move down

In fact, most households have more than one credit card, and the average household has about four active cards, according to 2000 U.S. Census data.

FORBES: How Credit Cards Affect Your Credit Rating

It has about 2 million active users, and about 40 million people have either received a card, have a Paperless Post account or downloaded the iPhone app, they said.

WSJ: Paperless Post defies digital strategy with Crane