Dedupe for unstructured data....
"...Just think about a dozen office workers storing a copy of an email attachment on their home directories."
Well, those "unstructured" files are not deduped because they are precompressed files. To get to the blocks, the card would need to decompress these files, and reassemble them after dedupe. A whole mess and major performance impact, no system would dare to make. So the dedupe here is limited to non precompressed, unstructured files, which are not that frequent... Result? Zero effect from this deduplication on stored email attachments...
There is only one thing you can do to reduce unstructured files on primary storage and that is native format optimization. The truth is simple sometimes...