One thing I don't think many people have realised yet is that in addition to the cheap games and freemium model, Steam is selling other goods too, under the gui

One thing I don't think many people have realised yet is that in addition to the cheap games and freemium model, Steam is selling other goods too, under the guise of giving away virtual goods for free. These goods are given away for free - trading cards, for example. However, in order to actually trade them you have to transfer your money into Steam to buy them from another player. That money cannot be withdrawn, it can only move around the ecosystem and eventually get spent on games. Effectively, they have already made the sale, it's just a matter of waiting for you to redeem the money - or not. I find it interesting that people are willing to pay other users real money for these goods, when (I assume) they wouldn't be willing to pay the money directly to VALVE - even when this is effectively the end result. It's an extension to the freemium model in my eyes.