The one problem they have is that the majority of their instances include local storage, which would make migration impossible. So the best they can offer is a reboot so the server ends up on another host.
They could potentially do this on their second generation (M3) instances, as well as micro instances if they wanted to. However I'd guess that these instances are just a small percentage of the overall servers used.
> The one problem they have is that the majority of their instances include local storage, which would make migration impossible
True for AWS. Using VMware vSphere then this could be done with a shared nothing migration which moves compute and storage (vMotion + storage vMotion combined).
