Tenkar asked if you use henchmen and hirelings. We use them, and I like them so much I co-wrote a book on them.
If so, how do you treat them?
Personally, I think the "meatshields," "mine detector," and "potion drinker" approach shows the wargaming roots of D&D. In a persistent wargame setting, it makes perfect sense to risk your least experienced and least valuable resources on the unknown. In a game growing out of a tabletop wargame, where you are moving your characters like pieces and promoting them between expeditions when they do well and survive . . . doing anything but expending your pawns and husbanding your queens and bishops and rooks and such would be foolish.
But a lot of adventuring groups aren't run that way. It's more like communal exploration group with a mix of senior and junior members. The junior members aren't suicidally bound to the commands of the senior members. Even senior members who employ junior members may do so as additional forces, not as resources per se. A hireling isn't a 10' pole, even if you may need one to carry one.
I personally tend to run NPCs as people, so they aren't all that willing to take risks they weren't hired for. Or do things the PCs won't do. I liken it to officers ordering troops around - the hirelings are the troops, and react about as well as real soldiers do when an officer orders them to do something the officer wouldn't do. They react much better when led from the front. I've noticed that my players play that way, perhaps partly from my influence. They lead from the front, and generally expect that NPCs are willing to do what they're willing to do and not much more.
Admittedly, they've squared the circle by using magically summoned, utterly expendable resources. But for living NPCs, they put them in no more danger (and no more risk of automatic death) than the PCs. They treat NPCs as more fragile but less important PCs.
Of course, most of this changes for NPCs who are either magically compelled, or who were hired for a specific task. The lockpicker doesn't balk at being assigned all the locked doors. The potion taster sips away. The suicidal fool who signed on to "check for traps" by walking point doesn't worry when he's on point. But the default isn't obedience to foolishly dangerous commands.
Similarly laborers resent being pressed into the front line to fight, and often solid fighters protest when the PCs treat them as pack mules. It's a matter of what their job is, and what they charged for.
Close allies are more like PCs in our group, but then they tend to be expected to carry more weight and do just as crazy things as the PCs. Of course, they're in it for much more than a salary - they get a piece of the action, or are fulfilling a stronger, deeper contract.
You get into an issue of "send these guys, they're expendable" vs. "watch out for these guys, they're vulnerable." The first attitude is the hireling as meatshield and walking trap detector. The second is that henchmen and hirelings as junior but important delver.
Which do you, and your group, default to?