TL;DR: The number of bitcoin holders has just surpassed 2 million mark! The growth is happening in the holdings of 70 bitcoins or less, especially in micro-holdings of 1 bitcoin or less.
Great news. So Bitcoiners are now 0.03% of the world population. Imagine what could happen when 3% of the world population becomes Bitcoiners. The exchange value can increase by 10 to 100 times.
Don't get too excited. Some of the data used to support the 2 million claim has turned out to be false (Mt.Gox sources). This estimate is likely to be revised downwards, heavily!
I think the evidence points out to 700k-1M users but would like to hear comments on the methods and not just "voting on the results" 