It's a disconcerting thing to see a bicycle whizzing by too fast, or one that is keeping up with traffic for too long. It's one of those things that you know, from your own experience, that shouldn't be happening because you have ridden bicycles and you know firsthand how much work is involved in doing that and the person on the bike you're watching doesn't appear to be working hard enough.  
Well, that guy or gal zooming by while slowly working the pedals isn't loping along in the highest gear. They're riding an E-bike. An electrically powered bicycle.
Virtually nonexistent only years ago, I started seeing signs of them now and again but the manufacturers were entrepreneurial, widely scattered, or regional. These bikes weren't for sale nearby, is what I'm trying to say. 
And far as I can tell, this is still valid. E-bikes haven't yet caught on with the mainstream, and I know what the mainstream is because I used to live in a very bike-friendly town which prided itself on having numerous bike paths and trails and very few E-bikes were to be seen. If any townspeople in the country would've been onto E-bikes, it would've been those folks. 
E-bikes, if we can get into the technology here a little, have of course batteries and motors. These add weight, so the frames on E-bikes have to be sturdier than regular (or should I say 'old fashioned'?) bikes. As well, because of the extra weight and the fact that E-bikes move faster, they come equipped with better brakes. Disc brakes. The tires and rims on E-bikes are wider and stronger and the suspensions are more robust. Make no mistake about it- these bikes can move.  Because of that (and because riding a bicycle is inherently dangerous) more care needs to be taken when operating an E-bike than a normal bicycle. 
E-bikes can still be ridden like an ordinary bicycle, they come equipped with crank pedals and have ten or twelve speed gearing, but their extra weight means extra work for any rider solely using human power for propulsion. Some degree of electric motor engagement is always needed to assist the rider, which corresponds to the bicycle's effective range. I myself have never ridden an E-bike so I don't know the particulars of this tradeoff but by the looks of things, that day may be near. 
Very near. There are numerous super-slick You Tube videos showing the top E-bikes of 2018 (of ‘2019’ too, even if the year’s only ten days old) and you can see that these bikes aren't your old low tech, heavy, factory made let-'em-die-chained-up-forever-on-a-bike-rack-in-the-rain throwaway commodities. These things are like scooters, or motorcycles even.

And because they can outperform regular bicycles, they can be hazards to them on bike paths, the pedestrians that walk on bike paths, and the pets that pedestrians often take for walks on bike paths. I don't know how municipalities are going to handle those issues but they will have to, in one way or another, because these E-bikes are going to be new elements added to established, predictable-in-speed systems. The interaction of E-bikes and cars on city streets and sidewalks where there aren't defined bike paths is already disorienting for automobile drivers, who need to track them constantly. They're hard to spot, come upon drivers quickly, and don't require highly visible headlights or taillights.  

Let's talk about range. The Lithium-Ion batteries that power many of these bikes provide them with ranges of over 50 miles! This is incredible and means that people in most places can use E-bikes in good weather to get to work and back without depleting the battery, which is a commute game changer on a global level. No fossil fuel tank required, no license required, no insurance, no license plates or registration, and minimal road impact (the reason for all those registration and gas tax fees). All this for a price less than you'd pay for a beater car!
Theft might be the biggest danger in owning an E-bike but technology to disable them and track them might deter thievery. One model I viewed has a detachable battery. 
So- goodbye throwaway bike in the bike rack in the rain, eh? This is the kind of bicycle you want to take care of. E-bikes to me are an absolute no brainer. I wouldn't be surprised to see these things take over the existing bike market and become the majority of sales. With their durable electric motors, elegance of design, lightweight quality parts throughout, inevitable future upgrades coming in battery charge time and output capability, and the riding pleasure they offer, E-bikes are winners right out of the gate. The only thing lacking right now is people to fix these bikes, because they're so new, but that will be temporary. Gaps in any emerging market get filled quickly.  
In closing, an aside here that might illustrate the potentials of E-bike ownership. I used to work at a job that was about four miles away. There were three different ways for me to get to work and back. Choice A was to take the city bus, and taking the bus always means waiting for it. The bus stop was a ten minute walk from my house, and dropped me off right across the street from my job. It got me to work and back is all I'm gonna say about that. Choice B. was to drive my car to work, which was always an exercise in overkill. By the time I warmed the thing up, I was at work. The cost effectiveness of this was negative due to all the costs associated with owning, maintaining, and legally operating the car. Choice C. was to ride my bicycle (one of four I owned) to work. It called for physical exertion, which warmed me up in the morning, but after work I wasn't so much for working out. Had I had an E-bike then, and been able to whiz home in the warm afternoon without exerting any effort, while enjoying the scenery along the way (and not be stuck navigating rush hour traffic on the city arterials that lay on either side of the serene, bucolic bike path or back streets routes I chose to meander along) that would have been my A-list choice hands down.