For those unfamiliar with the area, here's a map from MapMyRide.com If you check the elevation profile, you'll see why 45mph is possible on the descent.

For the doubters who've been checking snopes, if it made snopes, it would be tagged as true, and it's not the first bear hit by a cyclist there.

Bears are not considered pedestrians under Colorado law, but they do outnumber pedestrians in the area. (I've seen more bears [n=1] in the area than pedestrians) There are a lot more deer in the area than bears, so that makes them a potentially greater hazard. The deer seem to get hit with greater frequency by cars. The bears are apparently better targets for cyclists.