Over at Jacket Copy we learn that the top 10 Kindle downloads are free. And, look, as someone who regularly creates free content (that is read by people who regularly create free content) I'm not saying there's anything wrong with offering an e-book for free. I think it can be a savvy publicity tool, and a nice boost for your numbers (clearly). But I will say that these are not bestsellers because they're not being sold.
So, yes, these are the top 10 Kindle downloads. But they are not the top 10 sellers. As the Jacket Copy post says, other titles by the same authors that are being sold (as opposed to being given away) are ranked in the mid-thousands, which really makes you question how good a sense you can get of what people like and what people take because it's free.
I vote we actually make a distinction between "most sold" and "most downloaded." Because most people I know stream movies they would never pay for, use Pandora to listen to music they would never buy, and, oh, use the Kindle to download books they would never purchase.