On LiveJournal, noted:

IMPORTANT

If you write books with homosexual characters, read books with homosexual characters, please look at this:

http://markprobst.livejournal.com/15293.html

Mark, Erastes, and Alex (among others) had their Amazon sales rankings removed over the last few days for The Filly, Transgressions and False Colours respectively. On enquiring about this, Mark was told the following:

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

For additional background and other info, please read:
http://markprobst.livejournal.com/15293.html
http://community.livejournal.com/meta_writer/11369.html and
http://community.livejournal.com/meta_writer/11992.html