I love Dropbox. I have it on every computer and make sure all of my friends use it.
But I store 10GB of music in my dropbox, and I don't want that on every computer.
I would gladly move that to zumodrive.
It looks like Dropbox's selective sync is right around the corner, which would fully handle that use case.
Actually selective sync doesn't fully handle this case. With selective sync you could choose not to sync down certain files to the computer, but then they aren't accessible at all. With ZumoDrive, the files are accessible but "deflated", meaning they take up no space but will stream and cache on the computer when accessed.
You have no idea how much I would love to backup my music to a solution like this, but I do not live in a place that provides me with a decent upstream connection. What kind of speeds do you get when you upload? It seems to me that 40KB/s is a bit slow to be doing full drive backups online.