Ok, so I just posted the "wall 'o text" on making money off the Auction House. This is just a thing I do for fun (read: pissing off dicks who irritate me) because I can afford to do it. One, if you are looking for a way to make people lower their prices so you can get something cheap, this is not the guide for you. However, if you want to cause someone's entire money-making plans to fall apart, read on.
First you need a target. I save this for people who have either ninja'd something from a raid or who are just being trade channel pricks. We will call this target Noobmark.
Now I go to the auction house and search for Noobmark's auctions and see what he sells a lot of and for how much. Let's say he is big on Arcane Dust and is making 25g a stack ( Not an actual value, just using it because it is an easy number).
After scanning for other Arcane Dust auctions, I buy up anything I can cheap. I do this until I have accumulated around 5000 of the item. Like I said, this is how I choose to spend my gold now that I don't really "need" anything. I am anti-social ass, so hate me.
Now for my favorite part: I wait until I see that Noobmark has just listed a whole bunch of Arcane Dust. Now I take just 1000 of mine and slam the Auction House with 1000 one item Arcane Dust auctions all set for a buyout of 10s. Yes, that low because I just don't care. Then I spam trade channel with something akin to " Noobmark is selling stacks of Arcane Dust for 25g on the Auction House....Mine are up for 10s a piece---1000 of them!!!"
Make sure Noobmark is on for maximum fun because not only is he spotlighted, but now as people with Auctioneer buy these items their Auctioneer suggested price will drop drastically and his will be WAY overpriced because Auctioneer stores values now if you do a search, not just scans anymore.