The sad truth about cage biting: It is the animals frustration over being caged. No matter how domesticated we make them, animals will always know that they are meant to have more room then they do in a cage and more freedom then we allow them. We do it for their own safety, yes, but that is why they do it. It is bad for them to do and some can even get harmed from it and I agree with the different ways to stop it.
Otherwise, my reccomendation to people who can do it is to let them out as much as possible. Whenever you have time to supervise, do it. Also, our one boy was so bad that he had sores on his nose. We tied small pieces of fleece on multiple areas of the bars where he bit and he got mad that he couldnt slide his teeth up and down them and stopped. We also added a TON of chew toys to that area so he has things to let his frustration out on. It worked pretty well, he doesnt do it anymore.