I think this is more another case of pretty incompetent people going into this (probably linked to the fact that a lot of proponents of bitcoin are in it for the ponzi-scheme like qualities of the current environment). Maybe we'll get some people who've taken an accounting class and a concurrency class(necessary but not sufficient conditions) to implement these exchanges one day.
The public ledger in particular could be used to establish a good amount of trust with an exchange (publicly-auditable). The only problem being that many bitcoin proponents buy into the myth that bitcoin allows you to remain anonymous, and that the exchanges should be built in the same way as money laundering services.
We'll probably see a lot of this so long as the current environment is based around bitcoin being some sort of investment vehicle like gold. Maybe if enough people actually start wanting to use it as a currency, the quality of these services will go up, and we can trust them a bit more. Maybe actually having exchanges bail each other out (see Japanese banks in the 80s/90s) and supplying safety nets would increase trust.