I manage an ongoing playlist of one-time-media via Dropbox. I download podcasts there, plus TED talks and whatever video I can wrestle from the internet's grasp for offline viewing, because it's much more convenient that way: no buffering, plus the network on my desktop is more reliable, faster and cheaper. Also because I am an adult who is capable of planning ahead rather than a pigeon trained to peck at shiny objects for instant rewards. I like doing it this way, because it doesn't matter if I'm on my desktop or my netbook - they all go into the one synchronised collection, which I can access anywhere.
The point is this: I process a lot of this offline media playlist via my phone, on my train trips home (trips towards work are reserved for reading my towering collection of second-hand paperbacks, which is another story). I don't like my phone being the Source Of All Truth so I don't just download them directly there, and Dropbox doesn't let me select the whole podcast folder to keep it in sync over WiFi only. I do this awkward dance of moving tracks to my phone manually, then deleting them when I'm done. I consider it a bit dangerous, in a way, because when they're moved out of Dropbox, my phone is the only place that holds them. Sometimes I want to keep them, because they were really good, which means copying them back off my phone again before I move new items on there.
What I would rather do is just tell Dropbox that the Podcasts folder is to be kept up to date on my phone at all times, and it is to use WiFi only for this task. Then I know all my podcasts will be on my phone automatically, and I can listen to a track there once, delete it there and know that it is gone from my synchronised desktops and online storage too. I want to use that Dropbox folder as a way of managing media on my phone remotely, and to know that it won't spend my limited mobile data quota to get the job done.
Often I worry that the way I use software has drifted too far from the original design intent, and that's why it has become awkward for me. This may be one of those cases. I've mentioned before that streaming is not an option, so if that's the official answer, I'd be disappointed. I need things prepared offline, and Dropbox is almost, but not quite, up to the task.
Mokalus of Borg
PS - I suppose I could use a regular folder sync program, like SyncToy.
PPS - It's still an extra step, but it might be less annoying.