Hmm...this is an interesting economy/gimmick. You get a free game for joining Goozex, but that's not out of Goozex's pocket; all they give you are nebulous "points" that are completely abitrary and completely valueless other than the ability to trade them for a game on Goozex. And, since Goozex itself does not provide any games, there must be someone else willing to accept said points for your game.
That means, unlike credit at an actual store, where if it decided to announce its closure within the next 48 hours, one would have to scrable to spend their credit before it was too late, but still be able to get something for their intangible pseudocurrency. Should Goozex announce its closure in a similar fashion, any accumulated points would become immediately worthless, because no one would agree to send a game in exchange for a currency that will blink out of existence in 48 hours.
Additionally, every time a new member joins, 100 of these currency points appear out of thin air; as they do every time someone spends money to buy Goozex points. Both of these have the potentail to sharply drive inflation, especially if a large number of people join and buy points but not offer games for trade.
But, the sale of Gooxex points: That's where the genius of the business model lies -- there is a one-way conversion at an exchange rate set by the company, and the company that takes the money and gives you the points to redeem for a physical product isn't actually the entity providing the product. It has a 100% profit margin on every game "sold," less server fees. Spending $40 for those 800 Goozex points for a hot X-Box 360 game? That's all pure profit to the company; the seller of the game is rewarded with this additional "buying power" that, again, may or may not be subject to drastic inflation, and could become immediately valueless should there be a sudden exodus of member of the site.
Meanwhile, though, my first experiences with Goozex have been pleasant, but in the mean time, mmm, food for thought, food for thought.