Yes, it's possible to quit on your own. I quit for over 5 years on my own (although I guess you could argue that I didn't truly quit since I feel of the wagon this summer, but that's another story. But still, 5 years on my own is still a significant length of time). There are many alternative recovery methods, AA works for many people and is the most well known, but it is certainly not the only method (I've found SMART useful). You can google effective alcohol treatment methods and spend hours reading, there are also many good books on the subject as well.
One of the things I found interesting in my reading is that cigarettes are usually considered much more addictive than alcohol, yet there is no 12 step program called "cigarettes anonymous." Many people who manage to quit smoking, do it on their own (and it may take them many attempts). I don't smoke, so I don't have first hand experience here, but I've seen people trying to quit. It's seems very tough, but eventually many people I know have quit on their own.
It's interesting that smokers, like alcoholics, may have to give up some friends. Think about how often you've seen groups of people standing outside an office building smoking. A group of smokers might include everyone from the CEO to the janitor standing around smoking and talking, it doesn't matter who you are, if you smoke you are part of the group. When someone quits smoking, they give up hanging with a certain group of "friends" (who only had smoking in common) much like an alcoholic will lose his drinking "friends."