I just think that every team's best player gets a little bit of "dark horse" Heisman love in September. But it's not serious talk, and everyone knows it. Even as the USU announcers were saying that a healthy Keeton could be a dark horse for the Heisman, they had to know that even a 5,500 yd, 40 TD season wouldn't get him into the conversation in November (Kase Keenum put up similar numbers at Houston in 2009 and wasn't a top 5 finalist).
Obviously, BYU has more cachet that USU - by a long shot. But even so, unless they're really challenging for a playoff or NY6 spot, Hill isn't likely to be seriously discussed. In fact, outside of Provo, all Heisman hype would probably be over by or before week 4.