I don’t see it as a problem. It’s quite common in Asia (Japan, China). As BarnacleBill said, “perfect teeth” seems to be more of an issue in America than other countries.” That is true. I think here in America, a person’s image has to conform to an ideal perpetuated by the media or else that person is deemed less attractive. But beauty and attractiveness is arbitrary. The image of the underbite is commonly portrayed in paintings and other artwork in traditional Japanese culture, and is actually viewed as attractive, or at least appealing. It is a non-issue. But of course we live in America, where Hollywood and images of models seem to prejudice us to a certain image standard. Sigh!
http://www.apartmenttherapy.com/uimages/ny/prints22detail.jpg
http://www.accessjapan.co.uk/newlookimages/art/Kunisada1760.jpg