What I mean by competition is that when ever there is a real competition with a massive potential pay off, people go crazy trying to get it. I have no problem with some hackers trying to work the system here and there to try and steal a bit. You are right about incidents like that promoting overall security and helping seal up vulnerabilities.

But where there is a potential of millions of dollars as a pay off, then its not just one hacker trying to get in, its potentially hundreds of hackers. We have seen what a single group of hackers can accomplish when they attack an exchange. Now imagine 10 or even 20 groups sending out attacks every day for weeks or even months trying to break in. What will that kind of series of mass attacks do to the network?

And if you read the white paper I referenced earlier, you will see why they are very likely to succeed. 

PS I do want hackers to succeed in some areas. There is a lot of work for hacktivists out there, I just don't want all the attention on Bitcoin.