It's not that easy, but it's not exactly difficult, either. I've seen more complicated baking recipes. The hard part is not having the DEA kick down your door, shoot your dog, and throw you in a cage.
I haven't made hard apple cider that way, but I have made apple cider vinegar that way -- press the apples and put the juice in a jar covered in cheesecloth, to let the oxygen in, and wait a month. The wild yeast converts sugar to alcohol, and the wild acetobacter converts alcohol to vinegar. For alcohol, everything else is either about improving the flavor, or reducing the risk of infection.
Personally I wouldn't risk the DEA either; but a lot of people would -- particularly if it seemed like "everyone else" was doing it too.
Personally I wouldn't risk the DEA either; but a lot of people would -- particularly if it seemed like "everyone else" was doing it too.