Edmund Lee and Danielle Kucera, writing for Bloomberg:

As of October, 3 million to 5 million people subscribed to Prime, a program begun in 2005 that provides two-day shipping for $79 a year, said the people, who asked not to be named because the figures are private. Amazon is working to reach 7 million to 10 million in the next 12 to 18 months, the people said. Analysts have pegged the current number at 10 million or more, with expectations for it to climb higher this year.
That's really too bad, but the analysts did have some very high standards. Still, less than or equal to half of the expectations isn't that good of a turnout. Hopefully things will get better for the online superstore.

Via The Loop