In the US, it is typically the bank. However, if the bank can show that the merchant was negligent, then they can make them responsible. I used to have a merchant account and once in a while if there was a fraudulent charge found, we would have to prove that we followed some basic steps (checked ID for in person purchases, shipped to billing address on card, etc.). Once we submitted proof, it was accepted every time and we were never held liable.
I believe the new chip cards are simply an extension of that. If a merchant doesn't adopt the chip terminals, then the banks are going to make them responsible for the loss. Even now, the adoption of chip technology is uneven. Just about every store has the new terminals, but only a few use the chip slot. I've found that stores that sell higher end items like electronics (and Target) make you use the chip. Grocery stores around me always make me swipe. It makes sense, grocery stores do higher volume small transactions where the speed of swiping outweighs the more secure but slower chip (if they take a loss it's likely on a smaller amount).