There is some, albiet limited, use: a) It protects your data from hard-drive theft. Not an especially common occurrence in Amazon or Google scale datacenters b) It segments out the storage admins at your cloud-hosting provider from being accidentally granted access to your data. Useful from a principle-of-least-privilege standpoint.

I wouldn't quite say it does nothing, depending upon where in the stack the encryption is performed. If it's in the application layer (e.g. similar to transparent data encryption with SQL Server), it would stop anything else in user or system space from seeing the data short of hacking the DB process. Though it seems this isn't the case given that they're doing backup encryption separately and later.

They also talk about in-network encryption, which does directly speak to the NSA issues.

All of it is under the auspices of "network security", which is a growing concern because of the NSA debacle. And to answer ohm's comment, yes many people who know tangentially about the NSA accessing data don't really know that much about the practical applications of security. Something like this absolutely helps them drop a bullet point declaring security to bolster their cloud strategy.