Re: [STORE] UO Gold
As pibby said, there's a difference between items and gold. The more of a particular object there is on the shard, the less it's worth. If you can buy special, UNIQUE "donation items," then they do not readily impact the value of other things much, but they may SLIGHTLY increase the value of gold.
If you sell gold through the store, that outright (and very rapidly) increases the quantity of gold in circulation. This leads to what's known as "inflation." Yes, in-game economies follow all of the laws that govern real-world economies that focus on real money rather than pixels.
That said, I'm in favor of not selling money in the donation store. I do like how it's arranged that you can only get items that are NOT disbalancing, but still unique.