Philip Elmer-DeWitt for Fortune.com on how many Kindle Fire tablets are being returned based on Amazon reviews:

There were 3,678 write-ups in all, nearly half of them (47%) glowing five-star reviews that basically said the same thing (Typical headline: “Outstanding value at $199”).

What interested us, however, were the 491 (13.3%) one-star reviews. They are relevant because the number of Kindle Fires being returned to the store is likely to be an undisclosed material factor in Amazon’s results this quarter

Amazon got the media ecosystem aspect right with the Fire, but as I mentioned in my brief review, everything else was a big letdown for me. But I’m also someone used to the smooth, well-thought out user interface found on iOS.
Which leads me to speculate if many of the negative reviews of the Fire are from iPad owners who have higher expectations than from people who are buying their first tablets.