Well they had/have a huge opportunity to start an entire series of cottage industries like this but have completely failed to grab onto the idea. It seems like a pretty obvious extension of the "put a bunch of files in the cloud and sync" notion to me. After all, what's an app server but a bunch of program files stuck on a server drive?
I must say I do like your auto monetization angle though. If carousel is anything to go by, their 'we build UX ontop of your content' execution is so far a bit meh.
Trouble is, as Twitter showed, there's no long term joy in building a competitor to a service using its API.