Sep 5th 2008 9:53AM What is the guild bank for?
If your guild is a small, friendly, non-raiding bunch of people, you will use it to share your unwanted green drops, surplus reputation items, whatever. So it is just a place to store items too valuable to vendor but not too valuable to bother AH-ing, etc. (like my mum says: "It will be useful later for something...", and you realize after 20 years, that it was not.) In this case guild tax does not make too much sense.
If you are in a HC raiding guild, guild bank is for storing epic stuff, and gold for repairs. If you take a closer look, just consider one MH run. You got items from bosses (Void crystals after a few run..), receipes, BoE epics, and tons of epic gems as well. Even if you give anybody 2-3 gems for all of his new loot to socket, and enchant the gear as well, after a while you will end up with hundreds of unused epic gems, void crystals etc. in the guild bank. Sell 2-3 gems and a couple of void a week in AH, and all your costs are covered for a weeks raiding including repair, food, flask, potions and other consumables. It is much better since everybody was there when your guild got its hands on this loot, and nobody will ask a def warrior to put in 200g in form of any tax, when his repair bill is huge while in the meantime a hunter got a 10g bill.
If you are in a guild, especially in a raiding guild, and you actually reached something, you do not need tax to be financially sorted. On the other hand, i think you've never heard about GM transfering with the GB in a SERIOUS raiding guild. Pointless to mention the guilds made up by wannabe brainless kiddos.
I am against the tax.