A distinction needs to be made between a pedal assist and a "throttle bike". With a pedal assist you don't go roosting around and riding uphill at the same speed you descend and the negative impact on a trail is about the same as any other mtb. Bikes where you can simply throttle up and blast away fall more into the e-motor bike category for me and I whole heartedly agree that they don't belong on no-motorized trails.