It would destroy peoples confidence in bitcoins and the market price would plummet so effectively be worthless. Besides, he's is already making a truck load off transaction fees.
and yet the sheeple still continue to pile all their money into one exchange. i swear it is going to be our own stupidity and love for huddling together in one spot that kills this project. hopefully by the time the next decentralized currency comes out people will have evolved enough to realize why one exchange with 90% of the currency is RETARDED!! haha, maybe our collective subconscious knows decentralized currency is for some reason fundamentally unwise and so we are sabotaging ourselves.. cmon people, do whats smart, not necessarily what everyone else is doing. if bitcoin teaches you nothing else, please let it be this - DECENTRALIZE! lol, i don't even know why i try anymore...
I understand where you are coming from, but people have a tendency to "follow the herd." It also has to do with the fact that mtgox was the first major bitcoin exchange and has built for itself a good reputation, and it is this reputation that ensures a constant inflow of new clients. Good for them I say! But I do hope that some of the other smaller exchanges prove their trustworthiness and that eventually we'd have some reasonable market share distribution. Worry not when there is money to be made new entrepreneurs will step on the scene and attempt to take a bit out of mtgox's pie.