how much does a person really need to know?

How much do we really need to know about each other? More than any other topic that has surfaced in the past three years this would be the one that is top of my list. Some of my favorite phrases:

I didn't know!
How was I supposed to know?
This asked about general topics (public knowledge), things that have been communicated both verbally and in writing multiple times. How can people expect to know if they don't take time to listen or read? I honestly don't know how you possibly can't know!

Why wasn't I told?
Why didn't you tell?
The words "confidential", "privacy", "personal space" doesn't mean much to some people. Some people don't want everybody to know!

I want to know.
I have a right to know.
No, you don't always want to know and no, you don't always have a right to know.
Sometimes deep down you already know what it is you crave to know. Sometimes you just don't need to know.

In this "information" age sometimes too much knowledge is exactly what we have and exactly what we do not need.

How much does a person really need to know?