they say the light from their cell phones would serve to guide them in an emergency
That reminds me of a kind of funny story that happened to me. Back before I EDC'd my trusty Ritterphotonlight with me, we had the power go out while I was at work. Well, I was not only at work, I was actually sitting in a stall in the men's room. Though some parts of the building have emergency lighting the men's room was not one of them. I was instantly in pitch black darkness.
Though it really wantn't what one might call a survival situation I did STOP (Stop-Think-Observe-Plan). I had one of the old PageWriters on my belt (the clamshell text pagers) and used the screen light as a flashlight. It was enough to ... uh ... finish up, wash my hands, and find the door. Even the halls were incredibly dark, but I managed to find my way back to my desk where I did have a flashlight waiting.
Moral of the story:
1. Don't get caught with your pants down.
2. Don't underestimate the need for some kind of EDC light source.
3. Even the glow of a cell phone (or pager) can make a big difference.
4. Proper sanitation (washing hands) is important even in an "emergency" situation.