Non-psychic debugging: If somebody's complaining that a collection should be empty but isn't, you might want to see what's in there
A programmer on the GHI team (yes, the same GHI team) reported that they were hitting an assertion failure using an internal library and asked for help debugging it. "Can somebody help me figure out which factory it is that did not get unregistered?" I didn't work on this internal library, but on the other hand I'm not afraid to look inside....