trag said:

Apple warns (warned) that it could cause logic board damage.   Specifically, causing a change in voltage results in a current which is proportional to the rate of change of the voltage, or vice versa.  So if you rip the plug out fast, you may cause a current (or voltage) spike which will damage ADB circuitry.

Click to expand...

I'd sdd the possibility of mismatched potential levels and ESD. No end of problems generated on that front in the digital world, especially so as the connectors are as directly connected to the ADB controllers as possible. Using a KVM switch keeps all the components involved grounded together. It also ensures that all connections involved are broken and made as close to the same instant as possible.