ArenaNet's approach is this: Microtransactions are run on a currency of gems, which are purchased with physical-world money and traded in various quantities for the goods and account services available. Players also have the option of trading their purchased gems for in-game gold -- and purchase gems with in-game gold.
"If you want something, whether it's an in-game item or a microtransaction, you ultimately have two ways to get it: you can play to earn gold or you can use money to buy gems. We think that's important, because it lets more players participate on a level playing field, whether they use their free time or their disposable income to do it."As to the micro-transaction items themselves, O'Brien steered away from specifics. He mentioned things like visual distinction and expression as well as account services (which we saw plenty of in the original Guild Wars) and "time-saving convenience items" while adding that ArenaNet is opposed to the idea of requiring players to spend cash in order to maintain an even playing field.