I'd be curious what type of insight they're getting from markets such as China, India, Russia, South America and SEA. I couldn't find much on their site. Their estimate could still be relevant for their target market, while being completely off globally.

Also, only looking at public internet traffic is a mistake since this isn't solely where AWS is trying to compete. You need to consider _all_ hosting, including government, intranet and other private players, which AWS does attempt to capture.