Someone posted this to a discussion group about Great Pyr's that I read every so often.  I thought it was good and should spread its distribution a bit farther.  I believe they credited it to a Great Pyr rescue in Texas, but it sounds like it applies to every breed of dog, so I imagine this came from a lot of places.

10 Worst Reasons not to Spay or Neuter Your Pet

1. Just one litter and then we'll have Fluffy spayed.

Studies show that virtually the entire pet overpopulation problem stems from the "just one litter" mentality.
 

2. My dog doesn't run wild, so he doesn't need to be fixed.

There is no guarantee that your dog won't get loose at some time or another.
 

3. We always find "good" homes for the puppies.

Are your "good" homes going to be equally, or possibly, more irresponsible than you (e.g. not spaying or neutering the dog and letting it outside - thinking of the dog as a disposable pet)?  And what about all those puppies/dogs (and kittens/cats) already in shelters waiting for good homes?
 

4. I want my children to witness the miracle of birth.

Are you then going to take your children to the pound to watch those puppies be euthanized so they can witness the tragedy of death?  Seventy-five percent of animals that end up in shelters in this country are euthanized.  Ask yourself where your puppies will end up when you can't find homes for them all.
 
As far as learning about birth, go to your local library; there are books and videos about the miracle of birth.
 

5. My dog is so cute and unique; there should be more of her.

Have you been to your local animal shelter lately?  They are filled with cute and unique dogs - most with only a few days left to live.
 

6. It's not natural.

There hasn't been anything "natural" about dogs since we domesticated them and began to develop breeds thousands of years ago.
 

7. I just couldn't look my dog in the eye if I had him castrated.

You're anthropomorphizing (i.e. giving the dog human feelings).  Your dog doesn't have a sense of gender in the way that humans do.
 

8. A female dog or cat should have at least one litter for health reasons.

Actually, even allowing a dog or cat to go into her first heat increases her risk of getting mammary cancer later in life.  This argument is indefensible medically and ethically.
 

9. Neutering my dog will make him fat and lazy.

Too much food and not enough exercise make a dog fat and lazy.
 

10. Fixing my pet will change his/her personality.

The primary influence on an animal's personality is the kindness and care with which it is raised.
 

Animals don't ASK to be born...and it is up to us to help people understand the responsibility that goes along with pet ownership. We can make a difference, you just have to want to.