n/t
Because nature abhors a vacuum.
Maybe because the vacuum cleaner sucks up all the stuff that they just spent so much time scattering and smelling up.
How would you like it if you had your nice smelly spot all marked out and surrounded with chewed up bits of detritus and someone came and ATE IT ALL?
It’s gotta be the noise. It’s very loud and persistent and I don’t believe it’s found in nature 
My dog hates all things that sound like vaccuums - blow dryers, oven fans, hydrolic mechanisms. It scares the bejeezus out of her.
Can’t remember who said this but…
“Some people thing that language is what separates humans from animals. But I don’t think that’s it at all. It’s the fact that we’re not afraid of vacuum cleaners.”
As to why they don’t like them, I think it’s a combination of the noise and the fact that the darn thing rolls back and forth on the floor, alternating between “attack” and “retreat”. To a dog, the darn thing looks, alternately, like threat and prey.
I’ll go with the sound option too. Our black lab bitch used to go crazy when someone was using a R/C car near her. The car didn’t have to move, so it appeared to be the servo noises when using the left-right control.
She actually got quite distressed, so we never used it near her again.
Definatly the noise - there also could be some high pitched sound produced by the vacuum that the dog can hear and you can’t, making it even more irrating to you canine.
maybe vacuum cleaners give off an ultra sonic noise that drives dogs mental? I had a cat years ago who use to climb the walls if he heard someone taking the cleaner out of the cupboard, and the cat I have now gets very grumpy if I bring the cleaner into the same room she’s in … I wonder does it affect other animals?
Don’t know much about dogs, but cats don’t necessarily dislike vacuums. You can vacuum all around the furniture the cats in this house are sleeping on and they probably won’t budge an inch. They only run away if they’re on the floor and you’re vacuuming in their direction. And no, they’re not deaf, either.
True, some cats run away when they hear the noise, but I suspect they were traumatized by someone with a vacuum when they were kittens or something like that.
It’s because we chased our dog with the vacuum when she was little. Yes, I know I’m going to hell. 
For some reason, the dog doesn’t mind hair driers.
One of my dogs used to LOVE the vacuum, following me around as I hunted down stray dust bunnies. However, he’d persistently get in the way, so I would scold him. Now, when the vacuum comes on, he takes a seat on the couch and watches all the action from a distance.
Well, I’m certainly afraid of vacuum cleaners. 
My dog loves the vaccuum cleaner. Actually, she loves to be *vaccuumed. *
I discovered this when I came home from vacation a few years ago. My grandmother had agreed to dog-sit while I was gone. I came though the door to find my grandmother humming cheerfully, using the vaccuum cleaner hose to sweep the dog.
“What are you doing?” I asked her, surveying this bizzarre scene.
“She’s shedding,” grandma explained. “I always do this when I’m babysitting her.”
As I stared, she said “Okay, turn around,” to the dog. To my amazement, the dog did so, presenting her other side, and standing perfectly still. She even lifted her front legs so grandma could sweep under them.
Now, when I vaccuum, she follows me around, butting the hose with her snout until I stop and sweep her with the hose.
My Cockatiel actually seems to enjoy the vacuum cleaner.
He becomes quiet and attentive when I clean under his cage (home - the door is always open.)