I believe that the dangerous difference is whether the chassis of a component is grounded, by the IC's, or not. I know very little about this other than getting the snot shocked out of me quite a few times over the past 30 years. The last time being when my amp had a faulty chassis ground. In this case touching the metal end of an IC and the chassis at the same time made a complete circuit which traveled from one hand, through my chest, and out the other hand. The amp has since been repaired and as I recall the wall outlet was not grounded at the time (due to a clueless electrician who did some work on our place). Another member has mentioned to me that not running a ground can sometimes create a deficiency in the bass response of a system, though I never did check this out properly as I was too busy being shocked at the time.
