This is a very dangerous question. Thinking like this leads to huge security vulnerabilities in important systems. A better question is "What is the worst thing that could possibly happen if this system were successfully attacked?" If the answer is anything bad, it is probably best to assume someone will try to attack it.

As for the second part of the question, are we talking about the same internet? Because the one I'm on appears to be full of technically savvy people with loads of free time.