Cloud computing scales the efficiencies, yes. It also scales the problems. And because of this, AWS is by several orders of magnitude the worst of my current hosts.
I have dedicated servers. No downtime in past year. I have a couple of cloud servers with rackspace. No downtime (although i don't recommend them). I have some VPSes with local providers. No downtime.
AWS? More than 24hrs downtime in the last year. Seriously, for someone trying to run web sites reliably - screw that. I'm not using AWS any more.
And don't even get me started on the apologists. "EBS slow as treacle? Well you should have been running a multi zone raid-20 redundant array! Duh!". "EC2 instances dying at random? Well you should architect and implement a multi-master failover intelligent grid!"
I used to be under some kind of crazy delusional spell that the above was correct and it was somehow my fault that I wasn't correctly adapting to AWS's numerous failings. Well, no more. Now I realise that I should just stick with the super reliable service I know and love from traditional operators. You need to programmatically grow and shrink your app server flock? Great, use AWS. For the other 99.999% of us - stick with what you were using before.