I don't know if any of this data is of any use or significance, but...
I calculated the Gini coefficient at the end of each month of Bitcoin's history. I did it in two different ways:
* The vast majority of Bitcoin addresses that have ever been used are now empty. They don't represent the "have nots", they're just addresses that have been used and discarded, and so shouldn't be included in the calculation. Similarly there will be lots of addresses which are holding change from transactions. I arbitrarily decided to throw away all addresses with a balance of less than 1 BTC for this first calculation.
* Then I calculated the Gini coefficient for just the 100 richest accounts at the end of each month.
The results are shown below, with the columns in order:
* the date. "Jan 09" means "the end of Jan 09"
* the total number of addresses in existence at that date, including empty ones
* the number of addresses with 1 BTC or more in them
* the amount in the richest account
* the amount in the 100th richest account (notice how this stayed at 50.00 for over a year)
* the Gini coefficient of the >= 1BTC addresses
* the Gini coefficient of the top 100 addresses
-date- addresses >1 BTC 1st - 100th richest Gini >1 Gini100
Jan 09 2,569 2,439 2775.00 - 50.00 0.04571 0.50862
Feb 09 5,975 5,642 9075.00 - 50.00 0.05064 0.71354
Mar 09 9,444 8,864 16675.33 - 50.00 0.05794 0.82048
Apr 09 12,893 12,120 21175.33 - 50.00 0.05715 0.85527
May 09 16,288 15,380 26675.33 - 50.00 0.05306 0.87075
Jun 09 18,528 17,534 30675.33 - 50.00 0.05118 0.87980
Jul 09 20,456 19,338 36675.33 - 50.00 0.05248 0.89165
Aug 09 22,021 20,741 44473.86 - 50.00 0.05617 0.90351
Sep 09 24,180 22,639 53974.86 - 50.00 0.06188 0.91664
Oct 09 26,311 24,366 61424.62 - 50.00 0.07208 0.92725
Nov 09 28,533 26,403 61424.62 - 50.00 0.07279 0.93164
Dec 09 32,611 29,818 61424.62 - 50.00 0.08352 0.92241
-date- addresses >1 BTC 1st - 100th richest Gini >1 Gini100
Jan 10 37,647 34,333 72374.36 - 50.00 0.08571 0.92339
Feb 10 43,329 37,262 72374.36 - 50.00 0.13683 0.88570
Mar 10 48,615 40,316 72374.36 - 50.10 0.16674 0.82492
Apr 10 57,806 42,661 72374.36 - 500.00 0.21059 0.71037
May 10 63,368 44,583 72374.36 - 630.00 0.24448 0.65747
Jun 10 69,540 46,963 72374.36 - 750.00 0.26638 0.62843
Jul 10 94,992 51,628 72374.36 - 1757.14 0.32583 0.56689
Aug 10 107,172 53,578 72374.36 - 2100.02 0.35365 0.52483
Sep 10 120,562 53,492 72374.36 - 3000.00 0.39915 0.46956
Oct 10 135,952 54,637 85000.00 - 3333.33 0.42841 0.46050
Nov 10 155,639 55,756 90000.00 - 4150.00 0.45464 0.43790
Dec 10 176,326 57,247 90000.00 - 5000.00 0.47592 0.38625
-date- addresses >1 BTC 1st - 100th richest Gini >1 Gini100
Jan 11 210,243 58,073 250000.00 - 5350.00 0.49987 0.47440
Feb 11 267,542 59,699 250000.00 - 5650.51 0.52439 0.47584
Mar 11 353,093 61,984 250000.01 - 5613.86 0.54646 0.45504
Apr 11 443,112 64,254 200000.00 - 6002.81 0.57161 0.46808
May 11 631,480 70,883 297000.00 - 6309.40 0.62830 0.49247
Jun 11 1,061,590 90,159 424242.42 - 6308.24 0.70803 0.52602
Jul 11 1,548,806 101,895 384587.42 - 6450.00 0.73473 0.50905
Aug 11 1,930,979 105,572 104895.01 - 7495.92 0.74448 0.41533
Sep 11 2,205,926 106,973 105000.00 - 6926.85 0.74847 0.45014
Oct 11 2,411,298 110,463 105000.00 - 7345.73 0.75422 0.44981
Nov 11 2,601,999 111,386 455501.30 - 6926.85 0.76065 0.51328
Dec 11 2,768,500 118,263 105555.00 - 6705.00 0.76137 0.41685
-date- addresses >1 BTC 1st - 100th richest Gini >1 Gini100
Jan 12 2,956,869 123,003 105555.00 - 7000.00 0.76883 0.42408