Speaking as someone who sometimes puts his back out and spends a few days hobbling slowly about, I shouldn't have to quickly get out of someone's way if I see them coming and they shouldn't be allowed on pavements.
Don't move for runners, bikes (shouldn't on sidewalks unless it's a kid) or these things. It's up to the user to manage themselves and prevent themselves from hitting and potentially hurting others.
I see these around here and there, more and more, and don't mind them for now but if we start to get a problem with users hitting people then I'll support a sidewalk ban on them.
(EG When I'm biking on campus, sometimes I have to stop down completely because of 8+ students taking the entire sidewalk for them)
Assuming you mean where it is an offence to ride on the sidewalk, I'll always choose angry peds or a penalty over getting killed by a coffee-drinking, cell-phone talking urbanite in their range rover. Or non observant lorry driver. Or bus running a red light. Etc.
Cycle a bit in a city and you'll change your view.
And before you start saying I'll be endangering pedestrians with the same outlook - no. Pedestrians have the ultimate right of way. If there are 8 walking abreast and don't make way when I ring, then so be it, I'll go at 2kph until it's safe to pass them. I'm not in a hurry.
That said, I see no reason why the people riding these things couldn't just move around other people. I rarely have problems with people on bicycles, because we can mutually avoid each other.
My impression was that bikes are generally banned because they move fast enough to cause serious injury yet are silent enough that pedestrians don't hear them coming.
They are quite often laughably used in shopping centers or and super markets mostly because allot of the pavements in London are horribly uneven which probably doesn't provide a very good surface for those. I've seen 2 guys on those things at Westfield last weekend arguing with a bunch of confused staff that didn't knew how to treat them.
I don't really get this device it doesn't help you to commute any faster, it doesn't increase your pedestrian commute range if you aren't fit to walk you won't be able to use one of those (they got quite a stringy weight limit, and require quite a bit of effort to balance yourself on) anyhow.
It's a bit funny to see fit and young hipsters pretty much using a 500$ mobility scooter...
However, on most pavements it is still an offence but 'some' cyclists choose to overlook this point.
Actually, there was a study in the UK a couple of years ago that didn't get acted on, but which demonstrated that pedestrian crossing lights in British streets allowed so little time for crossing that able-bodied teenagers had to hurry -- middle-aged, elderly, unfit, or handicapped people really need about triple the time.
The solution is probably a combination of the sensor-controlled systems showing up in newer crossings in the UK (IR sensors block traffic by setting a red light until the crossing is clear) and cutting down on automobile use in densely populated areas like urban cores. Ahem. (Hint: why should your one ton rolling steel status symbol trump anybody else's right to use the highway?)
A countdown which displays the time until the red-man is best for a balance of all users.
What's more important, each and everyone of us, will inevitably, at some point in their lives be very young, elderly or disabled. In fact most of us will probably be each of those things during our lifetime.
So it's not so much a matter of efficiency as accepting the fact that human beings are not born with wheels, but with feet and that they should always get priority, despite any misunderstandings about what the purpose of "efficiency" is in the first place.
That is quite simply not true. http://www.censusscope.org/us/chart_age.html As you can clearly see, most of the population falls in the age range that has no trouble walking at a reasonable speed. I don't have exact figures on how much of the population is disabled or seriously injured at any given time, but experience says it's not enough to make up for the fact that the very young and the very old are very very far from constituting a majority.
In any case, you can dispute the numbers and it makes no difference. People are not born with wheels. We need space to walk about. By convention and by law, the pavement is not for vehicles.
Despite that, I'm prepared to share the pavement with people on wheels but it has to be absolutely clear that it's not my responsibility to avoid them. It's theirs. They are the ones choosing to put me at risk, they should take full responsibility for it. And watch where the bloody heck they go.
Edit: extra word