This is an embarrassing and ham-fisted cataloging error for a company that prides itself on offering complete selection.
It has been misreported that the issue was limited to Gay & Lesbian themed titles - in fact, it impacted 57,310 books in a number of broad categories such as Health, Mind & Body, Reproductive & Sexual Medicine, and Erotica. This problem impacted books not just in the United States but globally. It affected not just sales rank but also had the effect of removing the books from Amazon's main product search.
Many books have now been fixed and we're in the process of fixing the remainder as quickly as possible, and we intend to implement new measures to make this kind of accident less likely to occur in the future.
Thanks for contacting us. We hope to see you again soon.
this is the form letter they've been sending to everyone who writes.
it doesn't jive with writers' statements saying they were told by Amazon reps that their books were being classified as "Adult material". source