I remember Jaycar trying to use a slogan of 'It's a coincidence, but it's not a fluke' for their multimeters.
Cheap analogue meters can be better in some cases since the current required to move the needle puts a draw on the circuit and can show up bad connections by the voltage drop. Sort of like using a test light and taking note of how bright it it.
Back to the printer, it's got a figure 8 plug on the printer itself (reversable, no earth), so it would be easy for an imbalance to occurr and come out through the USB cable. I was mainly wondering if this was common since its easy to leave peripherals unplugged and the plugs in reach of kids. It could get nasty.
On electric shocks, it depends a LOT on how dry your skin is. Normal skin is about 1k ohm (enough for an autoranging meter to make make you think that you've got continuity when you hold the probes on by hand). I can't remember off hand what wet is, BUT if they are wet with salt water, it's a lot worse again.
Before LED lights, I'd go catching prawns (shrimp) with a car battery and a 50watt light. The car battery was floated in an esky and towed behind you. My original light just had the wires attached to the terminals by rubber bands. Worked fine, BUT if they accidentally came off, there was no way I could put them on with wet hands, it was very painful.
And there are no RCDs in this old place, just fuse wire so it will blow a few seconds after I'm dead to prevent the owners getting a huge power bill....
I would upgrade the printer, but I want to wait for a 3d one, then I can print business documents on fake marble carvings.