Cider started being pasteurized in the 90's following a very sad incident of a child dying from unpasteurized cider contaminated with e. coli. The likely culprit was unwashed windfall apples gathered from an area also used for grazing cattle. In short: bad sanitation.
If good sanitation practices are followed, the risk from unpasteurized cider is negligible. Far less than, say, eating a fast food hamburger. There is no federal law mandating pasteurization of cider, though some states (notably New York) have enacted laws to enforce it. Even so, as Bill Watson describes in his book Cider: Hard and Sweet, producer fears over lawsuits combined with consumer fear of unpasteurized cider means that unpasteurized cider has all but disappeared in the United States.
And this is a very sad thing, friends, because as has been previously mentioned, unpasteurized cider is the bomb-diggity. It's like eating Wonderbread your whole life and then suddenly being handed a slice of Tartine's sourdough. The cider tastes simultaneously sweet and tart, astringent and a little bitter. The flavors are incredibly complex and light up your tastebuds. Suddenly, it makes sense why Johnny Appleseed would travel the frontier selling apple trees and why the new settlers bought them by the dozen.
Scout out your local orchard and farmers markets. Those are your best bet for finding fresh-pressed, unpasteurized apple cider. If you are concerned about the health risks, just talk to the farmer. Tell him or her your concerns and ask about how their cider was pressed. Trust me, they will be more than happy to tell you exactly how safe and wonderful their product is.
If you have a juicer, you can also make your own cider at home. Be warned, though: it takes 15 pounds of apples to make one gallon of cider. If you want to go this route, picking up your apples at a local orchard is going to be the most cost-effective means to cider happiness.
Have you ever tried unpasteurized cider? What are your thoughts?