Is it possible to generate a monopoly in WoW Auction Houses? According to Tobold's MMO blog, it actually is. Not that it's all that hard or anything.

Are there rules about hording or market cornering? Uhmm, not really. It's simple economics. High market demand = High market price. How do you do it? Farm, fish or mine a certain thing to your heart's content. Then sell it for a reasonable price. It would probably earn you enough for that epic mount.

The problem is, some players are hording blues and selling them for outrageous prices. This practice is not limited to blues but also for ores and gems. This wouldn't really net so much love from fellow players as it is somewhat on the bad side of commerce. Players can control market price by buying every blue that comes up that's lower than the market price they want.

Tobold concludes that if nobody buys from these sort of markets then players would stop doing it. Same goes for getting scammed.