There is no need to put a hard limit, just an effective limit by having a general wealth tax. Money flows to where money already is, that's inevitable in a capitalist market economy. There's no need to change that, but progressively bigger piles of wealth should be progressively higher taxed to keep them in check, thus ensuring a competitive market.

Edit: I guess I should have known mentioning wealth tax would get people nervous. But this is not about taxing your old grandma for her paid-off house. This is about small but increasing percentage, starting at maybe $1M-10M and really kicking in at $1B and above. You can then abolish dividend taxing (that's only fair) and perhaps income tax altogether.