It is only the positive terminal that is really weak. Although I does look like the negative can be dented too. It takes a fall on the head to dent the positive badly generally. When I dropped my SC64c on its head last week it dented my VTC6 quite badly. It was so dented it would no longer make contact on any of my chargers. Luckily, a little careful prying with a small screwdriver quickly fixed the problem.
I'm trying a solution on my Zebralights with pogo pins to hopefully prevent dented battery terminals if I drop them. So far, I haven't experienced any issue with dents, but why wait?
I bought some cheap adhesive cardboard rings for 18650 terminal insulators. I think they were about $1 for 200 of them. I stacked them over the positive terminal of my batteries, so that the positive terminal is now recessed. the pogo pins can still contact it, but hopefully the cardboard rings will take some of the shock if I drop the light.
I used 6 rings, stacked on each other, for a Sanyo GA battery. Its positive terminal is slightly raised, so I needed a thick stack of rings to make it recessed. I use 4 stacked rings on the Sony VCT6 and Samsung 30Q.
So far, I haven't noticed any downsides. The rings are slightly wider than 18mm, so they do make the battery fit more snug, but there's no problem getting the battery out of the lights. I could trim off a thin edge, but I don't think I need to.
As for the upside, I haven't noticed any. But, I don't plan to do a drop-test to find out!