While I agree that car driver punishments are beyond just light, you can't use that as guage on this one. If you did, pretty soon, no crime would have a punishment.

I think the punishment was fair. These guys didn't make a little "oops", they knew what they were doing. Trails that are marked for hiking only are marked that way for a reason and bikers need to respect that. A message was being sent by the punishment and valid message. There are trails that bikes simply don't belong on.

While I suspect the trails in the Grand Canyon are more durable than those up in tree cover north, there is also the cost of trail maintenance. We have a long distance hiking trail that is maintained by volunteers. Whether we want to admit it or not, bikes are harder on trails than people. I suspect that there are a few of those volunteer trail maintainers silently cheering and wishing we could do more than slap a $100 fine <sigh>only if they get caught</sigh>