Not particularly telling, but it may be of interest:
http://dnr.wi.gov/news/Weekly/Article_Lookup.asp?id=2820
http://dnr.wi.gov/news/Weekly/Article_Lookup.asp?id=2820
I can one of these for $2050 plus tax
http://www.trekbikes.com/us/en/bikes/mountain/singletrack_trail/farley/farley/#
If you are going that fast down a trail that you can't avoid a biker who more than likely could hear you coming 1/2 mile away, you are going to fast. What if it was a deer or a wolf or any number of other obstacles that are avoided everyday? what if was a stranded snowmobiler?