While an open source codebase might result in safer code because of the crowd sourced review, it also would mean more vulnerabilities got taken advantage of (since the hackers can see the code)
Egg on the face of Mt Gox? Sure. End of the world? No. They're doing the right thing - rolling back to right before the fraudulent transactions, and life will go on. They reacted quickly and are clearly trying to do the right thing. Many of those screaming that the sky is falling either have a vested interest in another market or don't understand how markets work. Markets 'rolling back' are not common, but also has happened elsewhere.
I believe BitCoin will be fine - but it's entertaining reading the frenzied panicked posts like it's the end of thw world. Hackers are a fact of life and hopefully when things are back to normal AND secured, Mt Gox will publish an overview of what happened and what they've done to improve things. Otherwise, folks will vote with their feet