[varikin]

I thought they changed that because someone found that if you added that hash to your Dropbox to your local Dropbox database/config, it would download the movie. And for a week or two, people were pirating movies this way.

Though I suppose Dropbox could still use the same deduplication while making it harder to link a file to your account.

[pronoiac]

I believe they broke that scheme using other methods, which I can't recall.

Edit: They changed how it works on the server side, without going into detail. It's discussed here: https://news.ycombinator.com/item?id=2483053