Not to sure what to make out of this argument. Experts from IBM Internet Security Systems, Juniper, nCipher argue that data encryption is a new class of DoS. The post says "It's a new class of DoS attack.. If you can go in and revoke a key and then demand a ransom, it's a fantastic way of attacking a business." This does not make any sense. If someone can get your private key revoked you would have a lot to worry about other than data encryption.
It also says "Another risk is that over-zealous use of encryption will damage an organization's ability to legitimately share and use critical business data". The storage is encrypted but the access is not, so I am not sure what sharing issues the post is talking about. The leading database vendors such as Oracle provides column level encryption where data is encrypted before it is stored but it is decrypted on-the-fly when accessed and it is very transparent to the user or to the application. Though a limited set of real-time data should be encrypted since there is an overhead of decryption every time the data is accessed and the physical and digital security of the real-time data store is much better than an off-line storage such as backup tapes . On the other hand the backups should always completely be encrypted because they are not supposed to be accessed in real time and there is a greater risk of loosing a tape from a UPS truck or get stolen by baggage handlers. In fact Oracle once considered not to allow taking unencrypted backups at all.
What really matters is the encryption strategy of the organization for the data accessed in real time and the data that gets backed up on a tape. Some simple key management solutions and the right decisions and governance can solve the supposed DoS problems that are being discussed. You could take any tool and use it a wrong way and then complain about the tool itself. Encryption is just a tool and an enabler and you have to figure out how to use it. If you closely look at the "experts" in the post they are into the key management business and want you to believe that your keys will be revoked one day and you might end up paying ransom and also risk your data so why not pay us now and buy our software.