I am also not sure whether the qualifier "artificial" conveys the right impression, as the dangers might come from an augmented human brain suddenly developing the capacity for recursive self-improvement, or some other creation that does not look like a collection of silicon gates.

The Singularity Institute (folks) does consider the dangers to be from the "artificial" things. They don't (unless I am very much mistaken) consider a human brain to have the possibility to recursively self-improve. Whole Brain Emulation FOOMing would fall under their scope of concern but that certainly qualifies as "artificial".