Right, but a third-party app that talks to both Twitter and Dropbox can integrate them both easily enough.
As far as liking third party clients goes, that's the sort of thing I'm getting at when I say that App.net doesn't solve what I see as the root problem with Twitter. Not liking third-party clients is just a symptom of centralization, and App.net just happens to solve this one symptom without addressing the root problem.
