I've argued that we might have to worry about dangerous non-general intelligences. In a series of back and forth with Wei Dai, we agreed that some level of general intelligence (such as that humans seem to possess) seemed to be a great advantage, though possibly one with diminishing returns. Therefore a dangerous AI could be one with great narrow intelligence in one area, and a little bit of general intelligence in others.
The traditional view of an intelligence explosion is that of an AI that knows how to do X, suddenly getting (much) better at doing X, to a level beyond human capacity. Call this the gain of aptitude intelligence explosion. We can prepare for that, maybe, by tracking the AI's ability level and seeing if it shoots up.
But the example above hints at another kind of potentially dangerous intelligence explosion. That of a very intelligent but narrow AI that suddenly gains intelligence across other domains. Call this the gain of function intelligence explosion. If we're not looking specifically for it, it may not trigger any warnings - the AI might still be dumber than the average human in other domains. But this might be enough, when combined with its narrow superintelligence, to make it deadly. We can't ignore the toaster that starts babbling.
The question is how difficult it is to jump from the stupid AI to the general AI. Does it require hundred gradual improvements? Or could just one right improvement in the right situation jump across the whole abyss? Something like taking the "idiot savant golem with severe autism" who cares only about one specific goal, and replacing the goal with "understand everything, and apply this understanding to improving your own functionality"... and suddenly we have the fully general AI.
Remember that compartmentalization exists in human minds, but the world is governed by universal laws. In some sense, "understanding particles" is all you need. And of course some techniques to overcome computational costs, such as creating and using higher-level models. -- With the higher-level models, compartmentalization can return, but maybe it would be different for a mind that could work not just within these models, but also to create and modify them as necessary, as opposed to the human mind, which has some of those levels hardwired and the other ones always feel a bit "strange".
Being good at translating thousand languages is not scary. Being good at modelling thousand situations, probably yes.