I wouldn't even consider wearing a helmet on a MB.But I live in a fairly small town and my commutes are fairly tame,also by law Azins are not required to wear one.I treat these very much like bicycles and I know I would never use a helmet on a bicycle.

I went out to L.A. last weekend,around the Long beach area and the traffic was so intense I don't know if I would be comfortable with a MB, I guess you have to use the sidewalk alot,didn't see many bike lanes where I was,definitely helmet area there........Peace