Take a look at the picture. Maybee that explains something, but I’m not sure really. (From the canetoad shoulder tut)
Don’t think there is a way to avoid the behavior, but probably ways of painting weights that minimises the problem. And then you fix it with something else.
You can use a multitude of things to fix the skinning artifacts. Blendshapes, latties, extra joints, influence objects etc. I would go with a blendshape (driven by the elbow rotation with a set driven key) on this one. Go to http://androidblues.com/ and under tutorials select Maya joint deformation tutorial. You don’t have to be as detailed a him for a good result. One shape for the elbow is often enough for a simple character.