I had a little time to burn tonight, so I decided to load up a box of 9mm. I load on a LCT so that task can take as little as 20 min or as long as 45 if I really take my time, which I do quite often since I have a podcast going in the background (Tom Gresham's Gun Talk). Anyway, about half-way through the loading process, I noticed that a case was empty after running through the powder/expander die. The hopper was still mostly full, but the powder must have "arched", "bridged", whatever you call it. I immediately ran the case back up into the powder/expander and this time there was powder. I weighed that and the next few charges and they were all within 0.1gr, so I finished up.
It would have been easy for me to assemble a cartridge in the middle of my run without any powder in it. More than likely it would not have resulted in catastrophe at the range or at IDPA, as it would not have cycled the slide, but it certainly would have increased that risk many times over. I always make it a point to look in every case before seating a bullet. On a turret press, that's easy to do since I'm moving slower. If I was loading on a progressive, I think I would insist on using some kind of powder cop in addition to looking in the cases, since things are moving so much faster. Stay diligent - don't get complacent!