This is so harmful, because Mt Gox has been seen as the main exchange by many people, despite being almost useless for withdrawing USD for many months. People should have been avoiding it like the plague, but it was still a large percentage of the market.

One lesson here is that an exchange shouldn't be used as a wallet, i.e. Don't keep funds there for a significant length of time. Put your usd/btc in there, make your trades, then take the btc/usd out asap.