r/Fitness does a weekly "Moronic Monday", a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here - after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn't seem unreasonable that other people might as well.
If the AI can talk itself out of a box then it demonstrates it can manipulate humans extremely well. Once it has internet access, it can commandeer resources to boost its computational power. It can analyze thousands of possible exploits to access "secure" systems in a fraction of a second, and failing that, can use social engineering on humans to gain access instead. Gaining control over vast amounts of digital money and other capital would be trivial. This process compounds on itself until there is nothing else left over which to gain control.
That's a possible avenue for world domination. I'm sure that there are others.
Worst case scenario, can't humans just abandon the internet altogether once they realize this is happening? Declare that only physical currency is valid, cut off all internet communications and only communicate by means that the AI can't access?
Of course it should be easy for the AI to avoid notice for a long while, but once we get to "turn the universe into computronium to make paperclips" (or any other scheme that diverges from business-as-usual drastically) people will eventually catch on. There is an upper bound to the level of havoc the AI can wreak without people eventually noticing and resisting in the manner described above.