According to The Times' NewsFeed, Amazon will now "make it harder" (the article doesn't seem to specify further) to purchase certain genres of erotica, apparently particularly works that focus on prehistoric bestiality (no, seriously). Amazon's response is apparently in response to this article from Kernel Magazine, a multi-part "exposè" on Amazon and other book retailers profiting on erotica.
Censorship of fiction, regardless whatever form that censorship takes (including merely trying to make purchase "more difficult") is always worrisome for those who believe it could lead to a "slippery slope" ripple effect. Erotica hasn't always been a driving force, or even currently a main driving force, of genre fiction, but some of the most prominent works of genre fiction today (particularly in more sensationalist news pieces) are heavily driven by the erotica aspect.
Books with erotica only as minor plot points aren't invulnerable to censorship either. The debate as to whether or not erotica has any true literary contribution becomes muddled and readers' tastes and values naturally conflict over the "art verses smut" conflict.
Much of the popular fiction right now (and in fact throughout history) has aspects that might be considered "erotic," even if only implied. As someone once said, love is perhaps the greatest story of all - but there is legitimacy to the "smut" argument as well. This controversy will remain extremely difficult to wade through, and many excellent books (and those who consider the "smut" to be excellent nonetheless) remain in a precarious position.
Thanks to Jagvar who originally brought this to my attention when he posted this on, of all things, OppositeLock. The article's opening image was provided by him. Also, thanks for screwing up my neat little image order there, Kinja. I'll go back and fix it.