Exactly. The Mt. Gox rates are currently being manipulated by a few major players. Even a cursory analysis can show this is true without a doubt. It's great if you're a trader and capitalize on it to make quick returns, but investors should have no illusion of a free market at work, the total BTC economy is just too small at this point, and the only short term way it can get larger is for bitcoin to increase in value substantially.
What isn't free about the market? Are you prohibited from participating? Are their barriers to entry created by the government? Nautral monpolies at work?
It is a free market. If profits are that easy for someone with enough capital the FREE MARKET will bring in more entities with lots of capital and that "easy profit" will be erased and the market will continue to gain liquidity and depth.
What do you think
There are a few businesses where it might be acceptable to lose 20-30% in conversion. If you count cash with a scale instead of a bill counter, you probably don't care about sustaining ongoing trading losses to keep things on an even keel.
We accept Bitcoins. We never lose 20% to 30% in the conversion. If you are smart you can float an hours worth of orders and sell an equivalent amount as soon as you get paid (0-confirm). 0% lost in conversion. If you want someone else to do it use bitpay and for 1.5% they will deal with all the conversion risk/complexity.
There's way to much of bitcoin's future riding on Mt Gox right now. If Gox gets taken down for whatever reason (several scenarios come to mind) the bitcoin credibility hit would be huge. When no single entity answers for more than 15-20% of total transaction volume we might see the beginnings of a real market economy here. Last time I checked the market doesn't move 30% in a fractional second.
While I am often an outspoken critic of the Gox for a variety of reasons this is just more of your "I don't know what the word free market means" nonsense. The idea that you need an exchange to have no more than 20% of the volume to have a free market is just stupid. Have you heard of NYSE? Nasdaq? CBOE? While today a lot more trades occur off exchange that always hasn't been the case and even today a significant fraction of the trades occur ON the exchange.