(to) have it all

Here's a nice expression that was popularized by the women's liberation movement of the 1960's and 1970's. 

Today's headline is this:

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If Marissa Mayer can 'have it all,' can you?
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Here's another headline with a slightly different take on the matter:

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Women (and Men) Can Have It All
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And this:

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Women Can't Have It All Because
Nobody Can Have It All

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But the expression doesn't only refer to women (and men).  See our next headline:

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Why America Can't Have It All
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Reading these articles, what do you think that "having it all" means? 

With reference to women, can a woman "have it all"?

Can a man "have it all"? 

Can America "have it all"?

And who defines what "having it all" means?