I always thought leaving the printer unattended was risky.
I have never printed overnight. Recently. I noticed that the bed was taking a bit longer than usual to heat up. Routinely I pushed in the connector to the 12 volts to make sure it is seated properly.
I noticed it was a little warm.

Was this normal, I thought?

After finishing the print I checked the connector and this is what I found.

The connection had been arcing and the connector had been melting.

I checked the connector and it was rated at 10A. The bed as standard would draw around 11A, Yes there might be a derating factor for a lower voltage,

I chose to change the connector for one that is not pluggable.

So I was right; is it really safe to leave a 3d printer unattended? Probably not.

Is using the internet to start a print while you are not home a good idea?
I am not even going to try!