It was, but I don't know why. I'm curious to hear if Heroku releases any information about how this happened. Heroku's DNS was returning a single 100.64.x.x address which is in a reserved range.
That article is quite old (from Jan 2012). Amazon's independent publishing platform has extensive checks for plagiarism and content that is freely available on the internet. I know this system was there at least 6 months after that article.
Source: I used to work at Amazon in Independent Publishing.