Amazon responds to email inquiries regarding the removal of sales rankings:
Thank you for contacting Amazon.com.
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.
Customer Service Department
Ham-fisted cataloging error? Right.
There are a few theories being reported, none of which I really believe (somebody in France misunderstood "Adult"? Yeah...right), but it's cool to see that the rankings are coming back.
I still think I'll use Powell's books for my on-line purhcases for the time being.