It appears that Amazon is concerned that free Kindle book promotion blogs are becoming too successful. A few days ago Amazon made a change to their affiliate program that is going to shut down several of the larger free Kindle book blogs (or at least radically change them).
The rule change now will make it so that any blog that has more than 20,000 free kindle books a month and less than 5% of books sold are paid books will no longer receive any Amazon Affiliate income for the month.
I do not believe that will affect Bookwi.se because I am not that big. But I am not sure because Amazon does not currently share how many free books are purchased through my Affiliate links. I assume that Amazon will have to start publicly showing this information so that we can know what is going on. 20,000 books seems like a lot, but it is only an average of 667 free books purchased a day. If every visitor or RSS or email subscribers gets one free book a day I could be very close to the threshold.