Game on!

[Voicecoil]

Y

The problem arises when one side of the supply is connected to exposed metalwork either deliberately or by accident such as touching a metal bench or via another piece of equipment plugged into a dis board fed from the transformer. This creates the risk of you contacting both sides of the supply at once.

......That's why SMPS engineers tend to work with one hand behind their back I guess!

Seriously though, the danger isn't that great as to get a shock off an isolated supply you'd basically need to be touching something live with one hand and something neutral with the other, which is likely a smaller risk than touching something live and leakage to earth via feet etc.. And of course as part of the procedure I've always gone through when working in such a way, you do a check that there's mains earth continuity through the iso. transformer, so that in this case the machine chassis is properly earthed.