Changing saw blades or router bits without unplugging your machine is an often overlooked “no-no”. The risk of bumping the switch and inadvertently turning the machine on is probably low, but certainly not worth taking chances.
As a reminder, I fasten my machine’s wrenches to the business end of the power cord using a piece of string. This way, I have to unplug before changing blades or bits. The string is just long enough to allow use of the wrenches without untying them. -John Cusimano