Wait, if he can push up the price, why bother with the first part?
Buying a better rate on Gox isn't practical, because it costs more than it gains*. So why dilute the gains from manipulating the market by first doing something that is a certain loss? Wouldn't it make more sense to skip straight to manipulating the market?
* - This might not be true under certain rare circumstances, and depending on the exact way the discount calculation is coded by the exchange.
Maybe this is a high-capital scalper trying to minimize costs over the long term. Maybe it's a business model that requires a certain rate to get off the ground. Maybe it's an idiot who hasn't done their math (although this is relatively unlikely). Maybe it's an early miner looking to get a good rate for a big sell-off, or a new fiat investor looking to do the same. Maybe it's two bots going back and forth, or more than 2. Maybe it's a HFT bot.
But these point to the same fundamental market truth - bots will rapidly become more dominant players than humans without bots.
In order to minimize the effect this has on small- to average-sized BitCoin users, the only potential solutions are:
1) Disallowing all bots on the exchanges. It is unlikely the exchanges will ever take this step, as bots provide their customer base with more options to pay fees.
2) Leveling the playing field by releasing open-source bots to the public with the appropriate documentation to utilize them. This is doable, but not simple.
As bots become available to the public general market behavior changes, which will scare off some investors. Others will join the market since they now have more powerful tools available to them.
But bot behavior (while ultimately definable by the end user) is inherently more stable than human behavior due to their programmatic nature. The more BitCoin users who use bots in the markets, the more likely the market will begin to move towards a stable price. The closer it gets to a stable price, the less risk taken by businesses who accept it as a currency. The less risk businesses take on using BitCoins, the greater the rate of adoption. The greater the rate of merchant adoption, the more real purchasing value BitCoins represent.
Even humans making flawed decisions through a bot do so in a more controlled way than humans alone.
Let's take the example of an early miner or hoarder that wants to cash out some (but not all) of their BitCoins:
Without a bot, that user merely sets a price point, aims for it, and waits for transactions to execute into their price wall. If they set the wall at a low price, they lose a ton of potential income, and risk causing a panic following a sudden price drop. If they set the wall too high or too strong, they show their hand and sway the market away from their target price to a point lower than they wish to sell at.
With a bot, the hoarder can sell off all of their BitCoins without causing waves in the market. The user would set a price point (or range, or average price point, or minimum price point, or moving price point), and the bot can place only the orders that will be filled immediately - thereby executing trades at a better sale price for that user without destabilizing the market and devaluing the rest of their holdings.
Let's take the example of a new investor to BitCoin:
Without a bot, that investor would follow a process very similar to the hoarder trying to sell. Set a price point, and buy into it. With a bot, the new investor can buy in at a price point they set, or an automatically determined one weighted against past performance and price history. The average cost per BitCoin of the investor's entry is lower, with the result of lowering the effective barrier of entry to new money into the BitCoin economy.
Let's take the example of a local BitCoin exchanger:
In order to get the best prices on trades, without bots an exchanger has to day-trade the market heavily or take on large extended-exposure risk by holding BitCoins for a long period of time while they are volatile. With a stable of bots to handle buying and selling, the exchanger can focus on meeting new clients or promoting BitCoins with their time instead of sitting in front of mtgoxlive.com.
Bots add to net profitability in any market. The only question is whether or not the BitCoin community will build a suite of functional bots for the general public to use, or leave them in the realm of the big money that already uses them to dominate the other world markets.