The top holder of Bitcoins is the unlikely named 1933phfhK3ZgFQNLGSDXvqCn32k2buXY8a with 111,111 units of the crypto-currency (up from 40,000 units in the summer of 2011) for a total value over $110 million. Perhaps most interesting is these 100 Bitcoin holders represent over 20% of the entire outstanding amount of the alternative currency.
The following 100 Holders represent 2.23 million Bitcoins of the 11.12 million total oustanding currently...
(click image for full list)
[3]
and the Number 1 Holder has been adding (though hasn't added since Feb 2013...)
[4]
And the concentration of Bitcoins has fallen from its early incarnation highs but has been static for recent months...
[5]
Source: BitcoinRichList [3] [3]