I was just browsing thru the source (online, I'm not at home) and as I read CollisionSkin.cs I remembered a part of code from the documentation (Basic World - Creating a Body and Collision Skin) which I read yesterdy in the train.
_body = new Body();
_skin = new CollisionSkin(_body);
_body.CollisionSkin = _skin;
My thoughts went something like this: Why isn't the last line in the CollisionSkin constructor? Why do I have to do that? Does it make sense to set an other random skin to _body.CollisionSkin? Can a body have more then just one skin by leaving _body.CollisionSkin = null and only setting the Skin's Body?