Just this week in Vantaa, Finland three 12-year-old girls piled onto one of those electric scooters you subscribe to with an app and proceeded to get run over by a car at a crossing, killing one of them
The app is supposed to have an age restriction but it's easy to bypass and you're not supposed to have more than one person riding on one, which people routinely ignore
I hate seeing kids and teens speeding around dangerously on those fucking things and then just leaving them laying around on high-traffic bike routes because they don't give a shit since they treat the scooters as completely disposable
Fucking awful bazinga-brained Silicon Valley-ass idea and business model. Actually, there are also bikes you can use with an app but curiously you don't see kids doing reckless shit with those, almost as if electric scooters were uniquely terrible 
Yes although to be fair to doublepepperoni, the other complaints mentioned are not contingent on this strange take.
A car is just the worst case scenario, but these things are routinely involved in other types of accidents as well
Are they prone to accidents on their own?
Where I am, they are a lot more stable than they feel while riding for the first time, they're very bottom-heavy, and limited to 25 km/h.
Anyone capable of hurting themselves on a scooter could easily do the same on any kind of foot-powered transportation.
Small front wheel + standing position makes them very vulnerable to hitting tiny obstacles and sending the rider over the bars head first into something typically hard and unmovable.
Bicycles on the other hand have a much larger front wheel typically and can roll over obstacles that would take out a scooter operator.