Of all the animals raised on factory farms, chickens are most likely the most abused. This is not new knowledge many people, books, and websites talk about how the animals are treated. If you read the books or visit the websites they will tell you quite a bit about how the chickens are tortured. The type of things you would find out about are: Overcrowding in too small an area, 10-15% dying before they ever reach the slaughterhouse, improper traveling conditions like over crowded wire cages during o below zero temperatures, Chickens cannibalizing each other, rampant disease spread from unsanitary conditions, cutting off the beaks to prevent them from pecking each other, cruel means of killing them, etc.
Of course not all places treat chicken in this manner. There are some places that sell free range chicken, or at least claim that they do, you can't really know whether the company is lying or not. Regardless of how the chicken is raised. Think about the number of chicken that have to die just to make a bucket of chicken legs.
I don't eat chicken. I'd like to say that my reasons are purely altruistic, but they aren't. The main reason I do not eat chicken is because I do not like the taste of chicken. A common saying is “It tastes just like chicken”. To me that is a reason not to eat it. Another contributing factor is probably because I used to have a chicken as a pet when I was very little (it was actually pretty mean to most people and liked to chase all the other birds out of the yard).
I've talked about how the chicken are treated, the massive numbers killed, and my reason for not eating chicken. There are other reasons to not eat chicken as well. Chicken are fairly intelligent. The chicken maybe stuffed full of growth hormones or antibiotics which long term exposure to it can be detrimental to humans health. There are diseases that can transfer from chickens to humans and some of the places raising chicken are a breeding ground for illness.
One site that you can get more information on this is http://www.kfccruelty.com/ which is mostly about Kentucky Fried Chickens animal cruelty.