check out
http://wiki.bitshares.org/index.php/Market_Peg

It's going to be much more fancy

http://www.devtome.com/doku.php?id=bitshares_-_market_pegging

So.. I'm very skeptical about BitUSD, BitGLD, etc.

How is the initial distribution of BitUSD going to occur?  Also, is there a fixed supply?  If so then is supply and demand forced to match price?

Too much demand and price goes higher than USD/BTS price, and people start dumping?