Ahh very interesting question! Are we talking on a global scale cross-culturally?

Does wealth cause happiness? Does being poor mean you will have a horrible life?
What is poor? Technically speaking on a global scale if you live in America with running water and a roof over your head you are the 1% of wealth in the world.
Rich and poor are relative terms. At the end of the day I choose to be thankful for what I have, not envious of what I do not.

I may have badly worded my OP but that's not what I believe at all. I don't think we should live in an equal society, nor am I saying that some inequality is necessarily bad. — Purple Pond

Glad we agree there!

i disagree. What happens when the economy is bad? People start saving and they don't spend it. This is where you feel the effects money not in circulation. If every rich person kept a lot of their money in banks and never spend it, believe me, it would hurt you financially. So yes, if bill gates gets richer the rest of society get's that much poorer. — Purple Pond

I disagree. The 1% of wealth in this country does not move the economy when it's up OR down. The middle class does. For example, a rich person buys 3 or 4 pairs of jeans at a time. That's it for at least a few years. The middle class as a collective purchases hundreds of thousands of pairs. Which one moves the economy? When the middle class has no incentive to spend is when we have a problem. But hey, If more rich people would employ them, they'd have more mulla! See where my affection for the rich comes from?

No we don't. Most of us have to spend a good chunk of the day working just to makes ends meat. And who do we work for? Richer people. We're essentially giving them our time. All the while the super-rich practically don't have to spend a minute working. They could just live off their investments. Not to mention all the people spending their time working for them. They have surplus time. — Purple Pond

We don't have the same 24 hours? We can at least agree on that as a stand alone statement.
I hear what you're saying. I think you don't take into account the struggles that the rich dealt with to become rich. It's my personal opinion that if you took all the wealth in the world and redistributed it evenly in a decade the same people that were once rich will be rich again. Why? They know how to save and spend their bloody money!
Also, have you ever seen a wealthy person work? (of course I mean one that has created and or maintains their wealth through labor... their will always be the few that live off old money) They work their tails off!! Most rich people could run circles around me with their work ethic. Productivity = success

So, doesn't that mean that people are inherently bad? — TheMadFool

Yes, man is "bad", and therefore capable of horrific atrocities.
Conversely, man is "good", and therefore is capable of amazing selfless acts.

Without acknowledging both sides of the coin you do not have the full truth.
The law is set up to discourage people from doing harm. (I see your point.. they play on the assumption that man is bad)
However there are also people who set up non-profit organizations to feed starving people. (these people can't be bad, and can only be seeing the good in humanity)
These are specific examples that serve as microcosms of the bigger picture. There is good, and bad. Their are people who set out with assumptions about both, but I would argue nobody is inherently bad or good. Rather, I would say each individual is capable of good and evil, and it comes down to individual choice. Could we agree on that?

In an fair [equal] society everyone would get the same amount of slices. — Purple Pond

Correct me if I'm wrong, but this assertion you make follows this line of logic; equality among society is good, therefore inequality among a society must be bad. I would COMPLETELY disagree with this. Everyone is different. Everyone has differing values, experiences, and perceptions that are all unique to their own individual existence on this Earth. Therefore, claiming everyone should be equal is preposterous! What good does being equal do? Where is the incentive to strive for a better life? Your sense of life purpose would greatly diminish.
What I believe this notion of equality is really getting at is the fundamental difference between the economic philosophies of socialism and capitalism. Both are not perfect, however capitalism is the best choice. In socialism you would want everyone to be equal like you're stating, so wealth is distributed as such. The only problem is is if I had $5 and gave 5 people each a $1 dollar bill the wealth would be distributed evenly, but where is the incentive for those 5 people to go make more?? In contrast, from a capitalist's perspective I would demand each person earn my $1 bills by providing me a service, product, etc. If one person is uninterested or unable to earn my $1 he should NOT get one. Capitalism creates incentive for growth. I WANT more rich people, I WANT big corporations, because guess what both of them do? They hire people!! I've held two jobs my entire life, and you can rest assured both of my bosses were nowhere close to poverty, and that's not a bad thing!
Nobody starts at the same place in life, but one's decisions will determine where they end up. This is the beauty of life. Nobody is the same.. We are all different. Inequality is beautiful, and should be embraced, not stifled with the thought of forced equality.

Money. There is a limited supply of money in the world (the money pie). When there are more rich people getting more money, somebody has to be getting less, namely the poor. — Purple Pond

This is totally flawed.
If Bill Gates earns more money today, how do I become poorer tomorrow? There is only less money in the world if I don't work hard, and choose not to take advantage of opportunities. There's no finite amount of dollar bills circulating around. I mean, it's not infinite, but it might as well be. In my opinion this is an example of a psychological case (I believe asserted by Ellis, but please don''t quote me on that) wherein one decides that outside forces are the cause of misfortune, or on the contrary one decides it is one's own self that dictates their destiny. The former leads to a highly neurotic life of self pity and victimization, whereas the latter leads to a highly industrious attitude, and a healthy desire for the betterment of self. The maddening part of all this is you get to choose!! You choose for yourself how you perceive the world. Will the world dictate your life, or will your life dictate your world?

Time. A disadvantaged person's time is worth much less than a privileged person. Therefore the poor have to work longer hours and get less pay (less of the pie). — Purple Pond

Again, I believe this is flawed.
We all have the same 24 hours in a day. Oprah, Bill gates and Tome Cruise are all successful (privileged) people. What got them their success? Is their time more magical than my own? Of course not. What separates these people is HOW they spend their time. Success in this sense, all comes down to productivity. How efficiently and effectively you complete various tasks will determine your relative success over time. I guarantee you all these people I've mentioned have worked 100x more productively in one day than I do in one week. That is why I'm not on their level.

Side note: some people begin life's journey as poor, and end up becoming some of the greatest success stories (Oprah Winfrey)
Others begin life as rich and choose to make bad decisions, and throw it all away.
Why is this? Struggle creates the prize. A caterpillar must struggle in the cocoon before it can develop wings and one day fly. The butterfly who is let go at a premature stage (as i found out as a child) cannot fly. There is purpose in life's struggle. Embrace inequality for it is just one form of struggle.