380,000 Kindles sold. That’s double Mahaney’s May prediction. And it’s an important number historically. “In its first year, that’s exactly how many iPods were sold,” Mahaney wrote. “Turns out the Kindle is becoming the iPod of the book world.”

But is it really? And on what sort of data is that pronouncement based? Amazon (AMZN) itself has disclosed no actual sales data for the Kindle. The company said only that the selection of titles available for the device has jumped 67 percent since its launch. Surely it’s impossible to extrapolate sales of 380,000 from that figure alone. So on what other data is Mahaney relying here? Just this, apparently:

1. An anonymous source recently told TechCrunch that Amazon has shipped 240,000 Kindles. That’s shipped, not sold.
2. Kindle tops Amazon’s Bestsellers in Electronics list
3. Kindle has more than 4,000 customer reviews, quite a few of them positive.

Not exactly an abundance of hard data, is it? Which is not to say that the Kindle isn’t well on its way to becoming the iPod of the book world, just that we won’t know for certain until Amazon tells us with hard sales figures.