I'm taking all Amazon sales figures with a grain of salt. Since there's no substance to the claims in the form of actual statistics, we can't really trust the conclusions.
As L. J. says, we don't know if they're talking units or sales or profit or what, exactly. Do free ebooks count as sales? What about all of those short stories sold separately?
The other big statistic I don't believe is B&N's share of the market. I know, I just have one book and it's in a particular genre and you can't extrapolate from that, but when I hear that B&N has 25% of the ebook market but my own sales are 20-to-1 or greater in favor of Amazon, I have to wonder.