What your failing to take into account is there are plenty of finite resources people want. For example Land. As your relative share of total wealth decreases then your ability to buy land where you want it also decreases.
Land is much less useful resource than before, despite all claims to the contrary. You can become billionaire without ever owning a single slice of land - something that wasn't possible not so long time ago. I have hard time seeing how you need any land more that it takes to build a modest house. Of course, you may want a private island - but that's way beyond "sharing the wealth".
