Leak of Salary Information in an organization

I had a call from a friend of mine, who runs a small organization. When we were discussing Payroll and its operation, he asked me if he could do the Payroll processing himself. On enquiring the reason (as generally his accountant handles it), he informed me that he is really bugged about the leak of information, comparison of salaries and the subsequent heart-aches and effect on morale.

Why does this happen in almost every organization? Inspite of the best efforts of the management to keep this information confidential, how is it that people have the information? This is a question that really amazes me.

Which brings me to another point. Should it or should it not matter to a person on what his peer is getting? Here are some points that describe various views:

1. Why should two people performing a similar job get different salaries?
2. Why can't the employer be fair / knowledgeable when they recruit?

On the other side
1. Why should an employee feel bad - he was the one who negotiated his salary when he joined?
2. If an employee was unhappy about his salary, he could have approached his Boss for a review. Why should he feel bad after knowing that someone else is making more?
3. What happened to "My work, My salary"? Why does someone feel more strongly that they should get higher after learning someone else is getting more?

My opinion is that it should not really matter what others are getting. If I think I deserve more, then I should ask for it. Else, if I am still unhappy, then I should quit here and move on. If neither of the options are possible, then I should learn to feel happy with what I am getting.

Does any of the below mentioned facts influence my opinion:
- I run a small company
- The current economic and Job scenario.

An interesting survey and discussion on a similar topic can be seen at this article on the BNet Blog.