Growling is one of the most important ways that a dog can communicate to the people and the animals around it that its feeling uncomfortable. A dog cannot turn around and say to you "I don't like that can you please stop" or "I'm really tired and just want to be left alone" instead he lets you know by growling.
Unfortunately many owners interpret the growling as the dog being aggressive and so start to punish the behaviour. What many people don't understand is that their dog growling is in fact a way of letting us know that we are doing something that makes them feel uneasy. A dog that growls does not want to bite, because he is giving you opportunity to change your behaviour.
Now punishing a dog for growling by yelling or hitting it for example is going to slowly lower the chances of the dog growling again. This for some is seen as a good thing, the dog no longer growls when someone goes to close to him when he is eating his tea or when a child starts playing too rough. BUT you have now lost one of the most obvious warning behaviours. The dog that has now been punished for growling, instead of giving you a warning and a chance to change your behaviour resorts to the only behaviour it has left; biting. The reason a dog growls is because it is under stress; either from a particular event, because it is feeling scared etc. A dog that is already under stress is then confronted by an angry owner who is yelling at them or raising their hand; he growls again to let them know he is not comfortable but this just annoys the owner more and so the dog snaps.
The same scenario can come about when a growl is ignored. It is important that both adults and children learn that dogs need space too. Take for example a parent that allows their child to jump on their dog and pull his ears and his tail; the first time the dog might tolerate it, after a while he may start to exhibit some growling, but the child is not taught that is inappropriate and the dog continues to be pestered. Eventually the dog learns that the growling isn't working and resorts to biting.
No pet owner likes their dog growling at them, but is important that we recognise WHY our dogs feel the need to growl. What situations make them growl, and is there anything that we can do to change their response; can we turn a negative association into a positive one. A great way to do this is to start a behaviour modification programme using counter conditioning or desentization. And remember if you need any help with your dogs behaviour contact a qualified behavioursit that uses positive reinforcement methods.