Bots have multiple IPs. For example, Google, Google crawler bot's IP is different and Google Adsense bot's IP is different. Adsense and Googlebot are always present at my forum.
It could be a random website crawling you, not just amazon. But their crawler may be hosted on amazon AWS
MetaURI API/2.0 +metauri.com is the user agent string that I get for that IP, and that will be
http://metauri.com/ crawling your Forum
AWS is used as part of DDOS attacks. I block their IPs.