I was only defining 'excessive wealth' as money, in the hands of one person that isn't actually 'doing anything' except going into his pocket, and more than can actually be used by said individual.
That is to say, money like Gates' that is 'working' in Microsoft is fine, while wealth that is simply being 'sat on' is not (such as, in the example above, multiple large private estates).
Likewise, the control is an issue. Gates, legally, can't just disolve Microsoft and become a hermit in a cave made of dimonds, but look at George Soros who dumped 10 billion US worth of British pounds onto the market, almost crashing the entire British economy (this event was known as Black Wednesday). He did this basically because he's an arsehole. In Tailand he's considered an economic war criminal.