Little Blue Lights on Disk Drives:

If you need to move billions of bytes of data a short distance, the best way to do it is to pick the data up and carry it. No network can compete with short distance hand-carrying, also called “sneaker net”, for such speed.

When the plane I'm working on lands after a test flight, some of its removable disk drives have billions of bytes waiting to be analyzed. One computer has more than a dozen removable disk drives, each of immense capacity. Each drive has a little blue LED on it that flickers when data is being written to the drive.

One night last week the plane landed, and the usual people were not there to remove the appropriate data. Three people crouched over the computer and tried to figure out which drives to remove. They did this by running the same program again, that had written data during the flight, to see which drives it was using.
“I think that light flickered!”
“Nah, maybe that one. Run the program again!”
After awhile they formed a consensus and yanked a few drives. I thought it was quite amusing that a plane with cameras that can “see” in the dark, ended its flight depending on the vague visual inspection of its engineers, but they didn't think this exercise was funny at all.