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.
