Well I actually thought the conversation had switched to helmets. grin
Now I don't wear a mouth guard either. Yet if I rode more back trails, or did bmx or any other the other stuff that had air time, I'd think really hard about it. She has actually come up with a good idea. Some of the studies I think it was with football in mind, had mouth protection as helping to prevent concussions.
Though I wouldn't be as quick to wear one to prevent broken teeth, if it helped prevent concussions I would tolerate that. I suspect its about like a helmet too. Once you get used to it, its not a big deal. Maybe there will come a time I will want to protect my tooth, and if I were competing in the x games I would. I just don't feel the risk, cost, reward warrants it for a street ride on a lazy back road, but I also am fully aware that it will be me paying the dentist.
I agree with you though on it not being mandatory, and in my opinion that should apply to helmets as well. Every time someone tries to legislate common sense, it NEVER works out very well. The longer I live the more I have become to know that Will Rogers was right. Common sense ain't so common, and in a legislative body is practically non existent.