Or at least most bloggers are reporting an inside source at Amazon to this effect.
"Well, this is the real story: a guy from Amazon France got confused on how he was editing the site, and mixed up “adult”, which is the term they use for porn, with stuff like “erotic” and “sexuality”. That browse node editor is universal, so by doing that there he affected ALL of Amazon. The CS rep thought the porn question as a standard porn question about how searches work."
In other words, a French programmer got mixed up and wrongly edited some keywords so that books that were merely in some way coded as sexual - such as LBGT works - ended up being coded as "adult" - which apparently in Amazonspeak means "porn" , and were thus removed from sales ranks. The error was then spread through every database Amazon uses in every country it operates, as they all update and syncronise.
My tech journalist mate Simon Bisson has written a useful post (slash dotted by being linked to by Neil Gaiman on Twitter - ha - but now hopefully recovered) about how we can expect this sort of glitch to happen more and more in large database operations and how cock up is much more plausible than conspiracy.
Of course there are numerous other explanations floating round the Web including clever code bombing by right wing Christian fruitcakes over a quiet Easter holiday weekend, etcetera. But I think there's a poetic simplicity about this explanation.
Last week the more nationalistic wing of the French government (ie Sarkozy) got unexpectedly beaten out in its bid to set up a "3 Strikes" system to protect the French recording industry. What better revenge to take than to mess with the rep of the biggest purveyor of Anglophone books in the world? :)