As Plastic Police stated, this is less about preventing the majority of in-person fraud, but getting rid (for the time being) card counterfeiting. Yes, it would be much more secure with a PIN and Americans have shown that we can remember a PIN as we all use Debit cards... the only difference is that instead of a swipe, you insert the card.

A year or two down the road, they will switch over to chip and pin, which will just bring another headache. especially for companies that decided to do EMV on the cheap and get a Chip and Sign only reader. Now they will have to purchase new hardware, but hopefully (keeps fingers crossed) most places will upgrade to readers that have pin pads.

It will also be interesting to see how much of our world-leading fraud will move to online with the introduction of EMV... or if it will remain stable and just cut out the in-person counterfeit fraud for the most part (which would be a pretty big win, but not as big as killing almost all card present counterfeit with chip and pin)