To be honest I won't have the time to search all of the guild either and find it unnecessary. But I don't know how the system will be implemented so I refuse to make a big deal about it.
It will be a trainwreck, until most people have a single GAH they use to buy and sell at. Prices will be monitored by somebody running a market price tracking website, and that's how and where we will find the guild to use, and the prices to buy and sell at.
What happens as a game continues is a few guys amass wealth and set crazy prices that bar new players from joining in and playing on an equal footing. Then goldfarmers have their work cut out for them (often it is them who control the market prices anyway). Regulation would completely prevent this inflation, both at the low end and high end of the market, with min/max prices set by game using base worth as the starting point - ZeniMax simply has to get the base worth right and everyone would have a stable market that doesn't require fragmentation in the first place.
I already told you, guilds will be disposable, and someone will monitor prices on a handy website we all look to. We will all lump together on a chosen GAH anyway, so all this will be for nothing. However, this does not change the fact that high prices will eventually be set by those who amass wealth, then goldfarmers run rampant.
One mega server for an economy is probably going to svck. Finding stuff will be easy but 98% of pre-endgame items will be selling for a copper over vendor price with in a few weeks. That's just to many people putting the same items in the same economy. I prefer small markets myself because then prices vary.
OP (if you'd read) contained a way around this.
We will join into a big GAH, that is inevitable. Prices will be monitored by some guy running a website, that is inevitable (unless the game is so unpopular nobody can be bothered with the effort).
Their attempt to control us by fragmenting the market will all be for zip.
People will find out who the big GAH is, and join it to gain access to a decent market. Buyers aren't going to be buying at the most expensive GAH - they will find the one with the best deals and the most items they want. Prices will be monitored through that website someone will make, so there will be no hiding who is running the most worthy GAH.
Nobody will be forcing anyone - people will naturally group together. This is not a real global economy - we are just one click away from each other in a game, so joining together will be one click away as well.
OP has a good idea that would bypass the need for fragmentation to occur in the first place, but failing that, people will ignore this attempt to change the system and we will be right back where we started.
if the AH system is only Guild AHs, it will mean every guild you r in has its AH content shown to you.
also means, the content is limited, and the prices will be accordingly to it.
we can pretty much think further and see that crafters will be sought after, and they will be paid for crafting a item they can make.
thus, people buy less finished producst from AH, and gather/buy resources from AHs more.
The only problem there is that MMOs make the "base" price (the price that NPCs buy items for) notoriously low. In fact, when you're getting into the higher tier mats the "base" cost to a merchant is generally lower than the cost you need to pay to buy the merchant sold items used to craft it. Will this happen in TESO? Hard to say they haven't talked about crafting much. But I can tell you that PCs who harvest the materials aren't likely to sell them for as cheap as the "base price" is going to account for.
Hopefully what ever AH system they end up with, will have a good filtering system, to narrow your search, as far as price's go, players will dabble until they find what the market will bare, there will be those that put crazy prices on items, does not mean anyone will buy them, but we have no clue what the game economy will be, how hard will it be to mass a fortune, credits might flow, credits might be slow at coming, until then trying to fix the ah economy is kinda like putting the cart before the horse.
I kinda gota figure that what ever they use will be kinda standard, they have to do a lot of work to make sure the ah can not be exploited, or cause items to dupe or credits to dupe, the ah system is not all that simple, I just hope it has features like most other ah's I have seen around most mmo's..
Unnecessary.
To get away with price gouging you would need to buy every reasonably priced alternative that other players put up for sale. Without infinite money you could quickly go broke.
Those who watch the market could see the sudden 'demand' for this item and not only ramp up production but also increase their prices, making you go broke even faster.
That would be why the base price would need to be set appropriately by ZeniMax. It might even be something that applies only to the GAH listings. Actually under such a system we wouldn't even need the fragmentation in the first place, so scratch that - it might be something that only applies to the AH listings.