With the current rules:
The peg works if it is impossible for *you* to predict whether the number of dollars you are able to get for your BTS will be more or less than the number of bitUSD the price feed will say your BTS is worth before you intend to get rid of it.
This should be sufficient to cause there to naturally grow “perfect” walls on any liquid asset/bitasset exchange, even if all these bad things are happening:
* the spread on the internal BTS/bit* markets is almost always wide and "off-center"
* Occasionally all feeds give a price that is off by a factor of a few %, but it is reliably detected and corrected as soon as it is public information (BTS holders might get burned by this though!)
* one entity has information that helps it predict feed values for a minority of delegates
* Exchanges independently manipulate external BTS markets
Anyone want to stop me from pursuing this thought?