It varies slightly by state, but many places you can have up to 750-1000 watts and up to 20mph unassisted on flat ground and still have a bicycle, meaning no license or insurance requirement. You'll typically pedal close to 20mph on flat ground. I find these limits to be reasonable.
Well bikes are a little bit self limiting which helps. Me an average biker can do 20 mph for a while. Buddies who race can cruise 24, 25mph all day. But they also have really good reflexes.
Normal guy first day on the bike and 75 pound overweight? He does about 12mph. Throw him on an ebike and he can do 30mph or more (depends on the speed regulator).
Overall I am very split on ebikes. Love seeing more guys on bikes. The more bikes, the more cars expect them, the more bike friendly laws, etc. On the other hand, biking is pretty cool. ebiking is more like motorcycling.
I beginning to see a few on the local multi-use trail (where motorized vehicles are banned). One even has a giant fairing and looks more like a tuk-tuk or e-car than a bicycle.
Right now, there are few enough that it's not a big problem. But, the tuk-tuk e-bike is larger than a normal bike, so it's hard to pass (or make a pass) and will do more damage in a collision. Some of them are faster than the average road bike - I've seen several hybrid-style e-bikes cruising at close to 20mph with the rider soft-pedaling.
You've hit the nail on the head. To a lot of people (myself included), they're more like electric motorcycles.
I don't really care if people choose to ride them, but there are already designated trails that allow motorized access, and poaching mountain bike trails is going to ruin it for everybody.
25kmh with pedaling (you can go faster, but the engine will stop assisting at that point) and 6kmh on just engine.
I keep seeing videos on /r/ebike and similar from USA where some yahoo has ordered engine and battery from Ebay or China that can push the thing way into motorcycle range.