I recently read that the world's two richest men - Bill Gates and Warren Buffet - said that the most important issue facing communities was the issue of economic fairness. To my thinking, there are at least two measures of economic fairness: distribution of income and social mobility.
The first, income distribution, is fairly straightforward. People are born with a variety of skill sets and abilities. Some are able to make millions per year and some can barely tie their shoes. It seems as though a fair economic system would let the folks who make lots of money keep lots (but not all) of their money and would make sure that everyone has at least the first two levels of Maslow's hierarchy (physiological needs and safety needs) met. Communism in its purest form is not fair because it doesn't let those who work harder or smarter or better keep more money. Capitalism in its purest form is not fair because it ignores the plight of the inevitable losers.
The second measure of fairness is social mobility - the degree to which those born to poor parents can and do become rich or those born to rich can and do become poor (and the middle class rise or fall as well). We want an economic system that rewards initiative, creativity, intelligence, and hard work. These character traits are not limited to second and third-generation wealthy, so we would expect to see some variation from generation to generation.
In an economy so dependent on knowledge work, a fair economic system depends on a fair school system - giving each child, no matter how poor his neighborhood, the chance to gain academic and vocational skills that could enable him to make as much money as someone born to affluent parents.