I was DMing Red Box Vancouveron Wednesday and the party was exploring a dungeon. Getting a NPC henchman to carry a torch is a pretty wise idea; they usually have the hit points of a paper bag and all. However, having the NPC henchman being your only light source can really bite you in the ass when a monster uses a fear effect and the torch carrying NPC (who runs faster than everyone else due to wearing leather armor) splits from the party to flee the dungeon with the light source. Although the cutpurse pup was eaten, it wasn't a total debacle as the "two 18s" hobbit only ended losing some ability points from a slit throat and the 3rd level dwarf also lost some ability points and had his left arm and leg eaten by troglodytes (Death and dismemberment table house rules).
In my experiences as a DM players are notoriously cheap with their lighting situation whilst underground. They try and BS and play dumb regarding their light sources; they try tying torches to or putting candles on their helmets; even if they're in the middle of the party they'd rather give away their left kidney that use one hand to hold a torch.
Although I draw the line at nonsense like attaching torches and candles to helmets ("It will pretty much get knocked off by every doorway when you're in a hurry or fall off in every fight... do you really want me inflicting nonsense like that on your PC?"); tip regarding playing when Blair is a DM: "Aside from exceptions for magic, FTL travel, and monsters, if it wouldn't work in real life it won't work in my game and/or will totally fuck over your PC in a pivotal moment." And yeah, I'm of the opinion that you can parry with a shield in your left hand or you can hold a torch in your left hand but you can't do both at the same hand (you have to hold onto the handle of the shield with your hand, see...).
Some people would say I'm not being fun, that I don't get fantasy, that I'm being a dick DM; I say that I'm expecting the world I DM to operate according to someting vaguely like the real world while also presenting the players with tactical challenges.
Now when I'm playing I take every opportunity to spam Continual Lights on pebbles and coins ("Hey party cleric, since we're going to be holed up in this inn for seven days could you make seven continual light pebbles? Thanks!"). I will actually forgoe carrying a shield to *gasp* carry a torch AND a sword. I insist that multiple members of the party carry light sources. And under optimal conditions in dungeons I do something I call the "Road Flare System."
Torches are dirt cheap; they burn for an hour; they illuminate as well as (or in AD&D better than) a lantern; and unlike a lantern you can drop them without burning oil getting everywhere. So I use them up like candy in dungeons. I throw a lit torch into every corner of a big room if we're going to be hanging out in it. If I think we're going to have to beat a hasty retreat out of a dungeon while we're on a focused penetration I may very well leave a burning torch every 30 feet along the exit route. If my PC is part of the "reserve forces" (which every party should have!) during a fight I'll spend a couple of rounds throwing torches about so the battlefield is clearly lit and we can perhaps see if anything is sneaking up on us.
In my years of DMing and playing D&D I've said a million times that "you need to always carry food, water, a light source, a means of igniting said light source, a ranged weapon, and a dagger/knife. ALWAYS." And there's nothing more hilarious than a PC dying because they didn't have a light source or they didn't have a flint and steel to light their light source. And I've seen that happen a ton of times.
In D&D your characters should die if they're not prepared. You need to think like a Boy Scout, a Boy Scout that kills monsters undergorund for their money.
If you are an adventurer going underground to fight monsters... don't cheap out on the lighting; that's seriously amateur hour clownshoes nonsense.