I was riding my local MUP about 3 weeks ago, on a section that has about a 1% upgrade and somewhat rocky and rutted but if you know what your doing there is a line that is smooth. I'm riding my hybrid at a reasonable speed about 14 MPH when I get passed by two elderly couples, each on an ebike. The ladies in particular looked a bit uncomfortable on the bikes and they were going too fast for the conditions but hey they are adults.
At this point on the trail there is a road crossing so you have to stop and when they stopped one of the ladies went down like a sack of horse feed. My thinking is that you get a sense that it is a bicycle and there isn't any such thing as too fast or that it is light enough that when you stop you will have no issues keeping the bike in the upright position but that isn''t always the case.
So I view the whole ebike thing as some machines go faster than they should and I would not be surprised if we start seeing a lot more accidents involving these things. The MUPS around here have said ebikes are fine to use but I see some regulation in the future. Between accidents and complaints and the fact that there is always someone that will modify their machine to get more speed I think will eventually see use laws or rules coming down the pike.