If you're implying they are crazy for doing so, have you ever lost everything and tried to redownload it all? It's a huge timesink, I tell you.
As for de-duping, Dropbox does this. When you drop a Windows ISO or the Office installer into your folder, it hashes the file and realizes 'hey we already have this!' and you don't have to upload it.
they encrypt all data and i dont think it would be wise of them analyzing their clients data for dupes...if somebody would get to know that their business would be gone.
When different customers use different key to encrypt the data, even if the source is the same, the outcome is different. So it is not feasible to do de-duplication across different customers' data, unless all of them use the same key.
