I have a Dropbox account - it's a great service and yes, handles file transfer better than the MobileMe account I also pay for. The Dropbox API being the
best way to get at those files makes total sense. But I can't think of a reason (that serves their customers) for it being the
only way that they provide.
Making those files accessible in third party apps is a two way street. And as we were reminded recently, when you upload files to any service you don't own, you don't know (and may not like) what they do with them tomorrow. Example: the recent changes to the Twitpic terms of service that
asserted commercial rights over the content their customers uploaded. Folks have also raised
privacy concerns regarding files stored on Dropbox.
Which is not to dismiss any of the concerns in this thread. I like Dropbox, I use it, and I can see why folks want it in our apps. I just hope that the folks here are also filing feature requests with Dropbox to make their files accessible through generic technologies. Support in our apps or no, it seems better for their customers.