Perhaps the bandwidth between (dropbox + all your syncing devices) is greater than what the conspiring client can provide, so such a scheme may still be beneficial.
I think they could just share the folder with you on Dropbox, allowing you to download it from there.
You don't need to "get" the file from anyone, you just need convince Dropbox to mark your account as having that file.
Maybe I'm missing something. What possible purpose (other than getting the file) could there be to convincing Dropbox that you have a file?
By "get" I just meant download directly, which could be slow and eat a lot of bandwidth. And then if you actually want that file in your Dropbox, you'd eat even more bandwidth doing the upload again. But syncing once from Dropbox is faster than downloading from someone else and then uploading to Dropbox and then waiting for your other computers to sync. And since you don't have to get the file from the original sharer, they don't have to have enough bandwidth to go around, just let Dropbox handle the copying.
Other than? "Having files" is the entire point of Dropbox.
>> You don't need to "get" the file from anyone, you just need convince Dropbox to mark your account as having that file.
That post made it sound like there was a purpose to having the file in dropbox other than getting it.