One of the Rackspace employees said the same thing [http://lnkd.in/m3cQhJ], but I disagree with the support argument. Even if you include AWS's Platinum support (guaranteed 15min response, see http://aws.amazon.com/premiumsupport/) it's an extra 10% of the monthly AWS bill so around $7K for 3 years in the example that was mentioned in the blog - which is still a lot cheaper than total Rackspace costs. I think it comes down to Rackspace not having reserved instances, which is why AWS is much cheaper (not support).