If you check a competing exchange, you will find that the price of bitcoins has gone from $17 to $13. How does that constitute a crash when the price of a BTC had fluctuated down to around $13 within 48 hours before the breach? This is a security breach that only affected people using MtGox to trade their bitcoins for USD, so the trust in MtGox has been undermined, not the trust in the entire BTC economy. Most traders will likely move over to tradehill.com or some other competing exchange who have hopefully learned some lessons from MtGox's failures.
The thing about currency is that if it is not properly secured, it can be stolen. When someone robs a bank or steals a wallet, do we stop trusting paper money or do we just work that much harder to keep it secure?