I'm a generally happy customer of Amazon Web Services. So when I needed to set up a VPN server, I figured EC2 would be a fine place to stick it. Unfortunately, this has some unintended consequences for VPN users whose browsing traffic gets routed out through Amazon's IP space.
Many high-profile sites (including Yelp and the whole Stack Overflow family) block access from EC2. This can lead to pretty unfriendly errors:
I've even seen a site that just breaks subtly when some assets load and others are blocked.
I can only assume EC2 is home to enough badly behaved crawlers and content-stealing bots that they ruined it for the rest of us. I've seen others comment on the difficulty of sending email from EC2 due to reputation problems, but I haven't seen much comment on this HTTP blacklisting. For me it's just an inconvenience, but if I was trying to build a search engine it would make EC2 unusable.