Who wants to stop technology?
First, there are the common labourers who spawned the Luddite movement. These people are kept alive only because they work in poor conditions for a little money with which to support their families. They fear that technology will put them out of work and out of food. Never underestimate hordes of starving peasants. (Extra points for pitchforks and flaming torches as they march on the factory.)
Second, there are the ecologists who fear environmental despoilment. This probably includes elves. However, elves (in Tolkein especially) have their own industries... they don't hurt nature, but everything they make shines with power. I think it was once described as 'not magic, and it confuses the elves when other races get all weak-kneed when they look at elven goods'. What does this mean? I think elves have their own resources, and the only reason they're not at the forefront of the happy industrial revolution is because it requires centuries of training and/or working to put this stuff together.
Third, there are the monsters that don't use tech, but stand to lose territory or power over it. Dragons especially wouldn't like this. If your common peasant-with-a-cannon decides that all dragons are evil (perhaps because he's been losing sheep to something with wings in the night?), then you're looking at a one-sided dragonwar, and the tech-users are in serious trouble. I think the monsters are the biggest threat to technology. A dragon getting on in years is invulnerable to ballista bolts, and if you put a shotgun against a Pit Fiend's head and pulled the trigger it wouldn't scratch him. (Both do 3d6 damage against DR 20 according to the DMG.) Grenades and bombs start to do damage, but explosives aside, I think the DMG laser rifle is the first thing that can scratch creatures of that power level, and look at the punishment one such creature can unload onto an entire army.
And let's not forget the jealous mages. They can get past high DR no questions with their powerful spells.
Frankly, I think that technology would either become a whole lot friendlier (possibly governed by dragon-enforced treaty) or become one side of a vicious, planet-scarring war. Here's one possible scenario about technology:
The gnomes invented it, the orcs refined it, and the humans perfected it. The Fuel Kingdoms, we'll call them, began a new age of empires, felling forests to build war fleets and house their burgeoning populations, not to mention find fuel for their fires. They burned fossil fuels and dug deep for coal.
The elves saw it coming, and told the humans in no uncertain terms to stay away from the deepest forest. So the humans left the elves alone; they knew from experience what happened when you angered an elder race.
Unfortunately, they didn't think too hard when they decided to make things safer for their citizens. The Dragon Patrols set out to rid the lands of monsters with high firepower - rifles, cart-mounted machine guns, even cannon. The flashpoint came when a copper dragon was killed for taking sheep in a remote valley - the locals warned the militia, but they wouldn't listen.
One hundred years later, things are bad... very bad. The dragons united against a common foe - technology. The technical nations in turn developed worse and worse weapons to protect themselves. Fire has claimed most of the fertile grounds of the world, and both the dragons and the technicals have been reduced to a mere handful of powerful combat groups. The elves have remained largely unscathed... but now they control the green regions of the world, and the dragons and technicals both want them for their own.
How's that for an idea?
Oh, and I saw Nausicaa recently (subtitled, of course - I've head bad things about the dub). That's got some interesting themes. If you've seen it, ask yourself: Who had the highest technology in the piece? The answer is quite interesting when compared to all this talk of war and conflict.
