Well OK, so I'll put the leads on the fuses to measure current draw when the car's key is out, and once I find something, I'll remove the fuse and jam in the leads instead to measure the actual current then.
Its still way easier than pulling the terminal and running back and forth, if all you're doing is wanting to trace a gremlin.
Besides, when you hook up an DMM set to the appropriate mA setting, you are introducing a near zero-resistance bypass into the system at the point of the fuse. The current will almost entirely pass through your ammeter instead of the two ends of the fuse, as current prefers a channel of lower resistance. You should be getting about a 99% accurate reading of the actual current flow in the live circuit, so even for academic purposes reading the current off the fuse would be correct.
Are my assumptions correct here?