They are everywhere here in Barcelona. You will always get dickheads driving them like....well, dickheads. But then you get dickheads in cars and on bicycles to. The scals will have a field day with them I'm sure.
That said I personally think they are great for the most part. Mostly they are privately owned here. You see more then a few young lads who have 'modified' them so they can go over the limit, and proceed to drive them around like pricks. But for everyone of those, you get 5 or 6 normal people using them to get around, from guys in suits on their way to work to old ladies with their shopping.
The main difference between here and home is the amount of cycle infrastructure, which makes it a lot safer to get around on a bike, scooter or anything else which isn't a car (you see all kinds of contraptions for getting around over here - and people are much less arsey about them then they would be at home).
Scooters primarily on roads, and, lets be honest, pavements if there is no cycle paths, then it might be a different matter.
Long story short, the UK needs to get its shit together in terms of transport infrastructure. It's miles behind most of Europe these days. Tabloid fuelled outrage never helps either.
Some innocent bystander getting badly hurt is my first thought. Ideal for drug running across town is another.
What could possibly go wrong?
Arguments like this I don't tend to understand, because that could go for any form of transport already on the roads (or pavements). In fact we already have a form of transport that completely dominates most cities, in the form of cars, that are far worse then anything else being used to get from A-to-B, in terms of their threat to life, their pollution, and their negative effects quality of life for those not in them
If anyone can point to any country where the death or serious-injury rate from scooter usage, or any form of alternative transport, comes even remotely close to matching that from driving, then maybe the argument holds weight.