No canon evidence to say that greater distance needs more power. Firstly, by our muggle rules of the universe, point to point transport should be impossible. That impossiblity has already been broken by porkeys or apparition. It should therefore be no harder to transport yourself a country or continent across. Really, when you think of it, distance should play no role in teleportation. It's not like you're running the distance or moving the distance. You're popping from one place to another, as if there were no distance between them. The whole point of apparition is that it destroys the whole meaning of distance.

Secondly, were we to say that greater distance required a superior portkey, there's no reason to say that this needs more power. It could be that (and when I say could, I mean more in tune with the way the HP world seems to work) you simply need to cast the spell better.

Obviously wrong. In OotP Dumbledore made a portkey for Harry, without showing any kind of strain or stress, from London to Scotland. The distance involved in this is easily enough to transport a person internationally, say from England to France.

Again, obviously wrong. Dumbledore made a long distance portkey instantly, without trouble, after a challenging duel. And the portkey went through whatever spells Hogwarts has on it to prevent them (possibly none, considering the third task).

I, on the other hand, see wizards traveling a lot.

Dumbledore flew on a broom from Hogwarts to the Ministry in PS.

Or, alternatively, it "went rouge" because Harry and Ron crashed the damn thing into a tree.

And provide to me canon evidence of charging things with power, or something running out of "magical energy".

You're just making stuff up now.

1. We already know that you can apparate international type distances.
2. We already know that you can easily and instantly make porkeys for international type distances.
3. Harry was a weak wizard.
4. Runes are just old languages, like us learning Latin or Ancient Greek. There's nothing magical about them, in canon.

 

Hmmm, I would say that it could be interesting if, rather than having a 'capital city' or anything like that, the wizarding world (and by that I mean internationally, as in every magic person in the world) has some sort of island (Bermuda Triangle perhaps) which is a gathering place, a place of trade and transaction, not of Government. I would see it as being a place ruled by merchants not by politicians, a place where you can find anything you need so long as you have the money. There would be respectable areas as well, which would be controlled by certain merchants, maybe policed by their own men, and there would be disreputable areas controlled by thugs and the like.

So its not a central Government for the entire world, its just a place where anyone can go, anyone can do business. Past actions from anywhere else are ignored so long as you have the money to purchase whatever you're needing or wanting.

 

If such a place were to exist I would have it centred on Egypt, the Middle East or Rome, since the Magical World is all about heritage and those places have a significantly longer history than most places (especially small islands off the coast of a new land).

Still, Capital cities would be as much a part of wizarding culture as muggle I would assume, since it has been stated that Wizards and muggles weren't always separated. Plus, it makes sense to have all the necessary goods in one place, because wizards are just as lazy as we are (perhaps more so, since most places are just a twist away). Plus, it also fits in with the arrogant nature of wizards in general. Just a way to snub foreigners with fancier stores and better merchants. I would guess that Gregorovich set up shop in one of the larger European towns, just like Ollivander has in London.

Aekiel

 

Do magical societies even need a capital? They'd be a lot less dependent on infrastructure than Muggles, and it makes sense that their government would be much less centralised.

 

It would depend on the amount of bureaucracy they have. Seeing that Mafalda Kopkirk was devoted to monitoring Underage Magic, and you had useless departments like Arthur Weasley's, I would say they have their fair share of bureaucracy.

And then services to cater to the bureaucrats, houses etc.

In canon, I consider Diagon Alley the 'capital' of the wizarding society in Britain.

 

That is debatable. I personally view his department as the link for the law enforcement and the obliviators. They track down the problems and if they can sort them out, they do, if not, they call in the other departments to clean up the situation and apprehend anyone who needs to be apprehended.

They are one of the departments that keep the magical world secret and thus, are a fairly important part of the chain.