Here it is: in countries were most people live on wages (that is all the countries I heard of), there is a natural limit for the total wealth an individual can have: a lifetime of average wages.
I would call this the principle of limited property, and it should belong to your (and my) country's constitution, nothing less.
Most people's property/wealth would not be affected by this principle. Just ask yourself if you, or your friends, would. And then doublecheck: if the average monthly salary in your country is currently 1000 monetary units, then your total wealth should be limited to 120 years x 12 months x 1000= 1440000 monetary units worth (assuming the expected lifetime of a human would be 120 years). Compare with how much you own now :).
Anyone who manages to pull such a wealth at anytime, can afford to relax for the rest of his life. If someone is 70 years old, he still has the right to the maximum wealth, although, most probably, he won't live that long to enjoy it unless he will gamble it.
When the average wage changes, so does the wealth limit, so if there is real progress in your surrounding society, you'll be able to have more.
Some consequences of applying this principle: - the wealthiest people of us would be more honestly concerned with the well being of the society as a whole; - they won't be able to twist the arm of your government as easy as they are doing it now; - monopolies would be harder to assemble, you need more wealthy people to control anything significant, and more people collaborating means a better society; - possibly the wealthiest people will move in countries were the average wage is higher at that moment, but that means they will give away the power they had in the state they grew wealthy, to a more normal status in the new state: some of them will do it, but most of them won't, it's not the wealth, but the power of influence it represents that matters to them; - a smaller distance between the wealthiest and the poorest in the country, which will make the life in that society less tensed.
Do you see other consequences? Express them.