I don't really have any experience on the big data extensions, but in general i think what they mean is:
1 - You dont need to protect the data on disk using raid, since the data is secured in the application layer. The statement only means the hadoop data, not the VM. If it only covers the hadoop data, then it makes sense atleast to me.
2 - If thinking that the application is to manage the data on disk, like some kind of software raid solution (a long shot comparison with ZFS, that want direct access to the disks), then the performance might be "better" not using a raidcard, at least you would be removing over head.
3 - If the two paragraphs above make sense, then I think it would be hard for say EMC to compete on price.
I might be all wrong on this, just my thoughts.