I don't really get it, are they only using the magnetic strip and not the chip on the card?
http://www.zimbio.com/Credit+Cards/articles/wqJ31IbmC13/New+...
(Visa & Mastercard are the biggest CC companies here. Hardly anyone has Amex, and Interac is a debit card thing that Square doesn't support.)
I don't live in a big city, but I travel a fair amount across the U.S. I have never seen a chip reader.
Though the new Visa PayWave/MC PayPass tap-and-go stuff is really quick and super-easy, but not many merchants have it installed yet.