You can't legislate good taste, unfortunately, so trying to throw people in prison for wearing their pants like they forgot to pull them up after their last visits to the toilet is futile, not to mention that a case could likely be made for it being Constitutionally unsound, since they aren't exposing anything obscene. Indeed, the only thing such people really expose, is themselves, to ridicule.
My fashion pet peeve is the trend for preppy guys to wear the ridiculous-looking bubblegum pink polo shirt with the popped collar. It's ridiculous; you look like you went shopping at the Bazooka chewing gum online store, and forgot to straighten your shirt out when you left the house this morning.