Here’s the letter that author Mark Probst received from Amazon when he inquired about why his YA gay-themed novel was removed from the sales rankings:
In consideration of our entire customer base, we exclude “adult” material from appearing in some searches and best seller lists. Since these lists are generated using sales ranks, adult materials must also be excluded from that feature.
Hence, if you have further questions, kindly write back to us.
Best regards,
Ashlyn D
Member Services
Amazon.com Advantage
Their “adult” policy also catches plenty of non-gay/lesbian books in its net, including Lady Chatterly’s Lover. Sigh. The same old censorship with a different face.
The ladies over at “Smart Bitches, Trashy Books” (they review romance novels) are attempting a Google Bomb. You can join in by linking to their proposed definition of “amazon rank”: http://www.smartbitchestrashybooks.com/amazonrank.
This whole thing makes me very sad. I’ve spent a lot of money at Amazon over the years. Recently, I’ve started ordering from Powell’s bookstore, because they only sell books. I was getting tired of the non-book clutter on Amazon. I guess this gives me a really good reason to move my online book-buying completely over to Powell’s. 
I’ve given up on Amazon too – all corporations eventually become evil in one way or another.