You said "bitUSD will closely resemble the value of the US dollar because people will be able to easily profit from it if it doesn't."
Could you elaborate more on this?
If the value of 1 bitUSD is less than the value of 1 actual US dollar, then it would probably be an easy decision to buy bitUSD above the current bitUSD market price (closer to the actual real life value of the US dollar.) When the bitUSD market corrects to match your position, you will have profited off of that price movement, and you end up with more BitsharesX than you started with.
If the value of 1 bitUSD is more than the value of 1 actual US dollar, then it would probably be an easy decision to buy bitUSD below the current bitUSD market price (closer to the actual real life value of the US dollar.) When the bitUSD corrects to match your position, you will have profited off of that price movement, and you end up with more BitsharesX than you started with.
I think Daniel explains the dynamics of trading better than I can in this document. I have not read it yet, so I apologize if I have spread any misconceptions. I do not think I have though... he just explains pretty much the same things in a different way.
For instance... I already learned something I did not realize. After quickly scanning over the document, it seems there is another protection from manipulation built into the market:
The ability to short and the price at which margin calls are executed is limited by a moving average of the price. There is a maximum rate of change on this price equal to 0.09% every 10 seconds. This averages out to about 33% per hour. These price restrictions do not apply to those selling BitUSD for BTSX, only for those looking to short or for margin calls. The purpose of these restrictions is to give the market time to react to potential manipulation attacks.