It turns out that Amazon doesn't like it when you host classified documents on its servers. WikiLeaks had been using Amazon hosting while publishing documents leaked to it by Chelsea Manning, and eventually it got cut off. Amazon later said it was simply a matter of WikiLeaks failing to follow its terms of service, which — in fairness — is probably accurate. WikiLeaks apparently
returned on other hosting later in the day. (I realize that this technically doesn't count as an Amazon service being shut down, nor an obscure one, but it's one of the more fascinating things that Amazon has shut down.)