Before I start my opinion I am not a trader or shorter and have no real interest in playing the market so to speak.
I understand that to create a bit asset you need to use btsx as collateral.
I believe most of this hinges on btsx basically holding some value. As the author puts it if btsx lost alot of value very quickly this would cause the system to close(I believe thats the term) on said collateral.
I understand that bitusd will be pegged through feeds to the price of usd(so they trade roughly the same other then the point of interest to bitusd), which in theory so give bitusd a edge.
I have been exploring the next forums and have been doing research on how their asset's work. Basically anyone can make any asset with no collateral and it seems to be based solely on reputation. I think it will be interesting to see how it develops but for the moment it is pretty ripe with scams. I did find it interesting that a company has been created and is offering a service to audit real world holdings so that digital assets have a little more weight(no pun) to them. I think its a interesting idea. Heck I would like to see a system that is able to use different kinds of digital assets(bitcoin, pts, nxt, whatever.....) and also has a mix where users can create their own asset, pay a company to come out and audit them for their real world holdings. Best of both worlds. I believe bitshares has the potential to do all of the above and more with the addition of contracts.
Please understand this is just my rudimentary understanding and feel free to correct me where necessary.....