I hear countless complaints about the income segregation of cities, ranging from the New Urbanists' declaring income diversity as a goal to the general complaint against "white flight" to the suburbs. That wealthier folks prefer to be next to each other is obvious, but what is not being asked is why they came to prefer this. Certainly there are cultural factors at work, that wealthy folks have more in common with one another and therefore attract each other. This factor however does not explain mass flight of the wealthy to the isolated suburbs, leaving behind their previous perfectly good neighborhoods.
The answer is institutional. An egalitarian democracy, where everyone without requirements may exercise a vote, is always a tool for the redistribution of wealth from a group of haves to a group of have nots. Since the haves are always a smaller number than the have nots, the haves can never exercise electoral significance. The redistribution may not be immediately evident. It does not necessarily take the form of direct monetary transfers from one group to the other. It can simply take the form of disproportionate spending in favor of the have nots funded by disproportionate taxing of the haves. Public schools are one such obvious form of redistribution.
The best thing for the haves to do in order to protect themselves is to isolate themselves in their own electoral enclaves and segregate out the low-wealth masses using regulations such as minimum lot sizes and house sizes, outlawing retail-apartment buildings, and so on. The electorate is therefore limited to the upper end of the income curve, and although there are still wealth redistributions between the extreme haves and the moderate haves, this redistribution is much milder than before.
In order to end this practice and bring about social peace and economic efficiency, it is necessary that the governance process be anti-egalitarian, that one's electoral power be based on private property. It could be done either through a system of exchangeable vote-shares, such as in a business corporation, or the number of votes one person exercises could be equivalent to the amount paid in taxes, such as in a condominium. This system would eliminate all incentives to conduct wealth redistribution and thus make the coexistence of the wealthy and the rest possible once again.