This is a pretty clever function, actually.  I guess I'm okay adding this. But add a comment before it explaining why you'd want to use it.  Basically, you've got algorithms that usually deal with Blobs, so your code depends on the BlobView API (not just the DataView parts) and you're stuck with an array buffer instead.

Also, is it actually useful to create the Blob here, or could you just pass null as the first argument?
That property is only used by getMore().  You could modify getMore to throw an informative error if the blob was null.