I do think of it as destroying local server economies, as it is impossible to even discriminate in favour of your own server because there is no safe way to trade with someone on your own server.
Yes it has created a global economy. But is that good or bad?
Yes it has destroyed a local economy. But is that good or bad?
Ideally for me, they can and should co-exist.
They can't and shouldn't co-exist, and the reason is very simple.
1)If you sell your stuff on your local "auction house", since there would be lesser stuff being sold, the price would be higer then the one of the global "auction house"; and no1 would buy your expensive things.
2)Even if the price of things was the same beween them, then the wole point of having two separate AH would be even more pointless.
That being said global AH is a really good thing, as some1 said before me, also because it liven the economy. If there are more people selling the same things prices would lower and you could buy more gathering mats or vanity items etc.