The problem I see with Coin from the start going forward is that the US is mandated to move its credit cards to the European standard by Oct 2015 or at least the major banks are required. So far from the prototype of coin it is still using just the magnetic stripe which eventually will be OBE. Would be interested to see if Coin is already on top of this and is already coming out with a way to implement the EMV embedded chip to provide "chip and pin" support to its Coin card.
EDIT: Read the Coin FAQ under the "Security" section for question 1 and it looks like the first generation Coin cards are designed to be used in the US market only. However they did mention that future generations of the Coin card will have an EMV chip with "chip and pin" support. Would love to see how the first generation users like the Coin card.
https://onlycoin.com/support/faq/
Q. Does Coin support chip & pin (EMV)?
A. Coin is currently designed for the U.S. market and does not support chip & pin (EMV), however, future generations of the device will include EMV.