What appears to have happened here is something completely unrelated to the technology. The same thing could have happened in any financial exchange.
There were two difference that made it possible here: 1) the investors may have been technical experts but were financially naive and dramatically underpriced the risk, and 2) the market was completely unregulated, so the financially naive investors had no protection from those who weren't so naive.
Denying their technical expertise is more interesting. I've heard that theory often, and yet there are plenty of people I thought were technically proficient who lost money.
Indeed, I have some (small) amount of money in another Bitcoin exchange - it is convenient.
Perhaps the level of technical expertise of these users is roughly that of an average HN reader: ie, somewhat higher than the general population.