I think that in some cases the loss of a pet can be so much more devastating because the pet can't take care of itself. You are the sole caretaker for that animal, often times you have to make the choice to put the animal down and you are left wondering if you waited too long or didn't wait long enough, there are so many questions that you may never know the answers to in the loss of an animal. Animals also (like children) are pure and innocent. I don't think it means we value life of animals over humans, just that it's an entirely different kind of loss. Comparable to losing a child over an adult.
Hail Gunther 7-2-2013
If at first you don't succeed, destroy all evidence that you ever tried.
"Some people never end up going crazy...what a truly terrible life they must lead." - Unknown