I think one of the reasons I have never considered using Dropbox for media storage is that, given three teenage daughters, I don't think I could afford a big enough Dropbox account to store all of the media we consume and generate.

Also, one of my favorite applications of Dropbox is having all of our important documents in one central location (whether this is a wise move or not... ). This makes accessing documents on the fly from my iPhone a breeze. Having media files in there as well, would, I think destroy my antique iPhone 3G!

You are right on the money about the background uploading though.