Dropbox, just like IPFS, allows users to access its content via its SHA-256 hash, regardless of which account uploaded the original file.
Imagine an IPFS node that, upon receiving a request for a block of data by its SHA-256 hash, would query Dropbox for that hash.
This would effectively put potentially petabytes of data, already addressable by hash via the Dropbox API, on IPFS as well.
I believe it may be limited to files less than 262144 bytes in size (because of how IPFS chunks data, and the IPFS hash may need to be hashed again to acquire a dropbox content hash for the correct content (https://www.dropbox.com/developers/reference/content-hash).
This could be as simple as getting the wantlists of all its peers, and running all the hashes through Dropship or something similar, and ipfs adding any successful Dropbox downloads.
Info on getting data from Dropbox by SHA-256 hash only: https://github.com/driverdan/dropship http://blog.fosketts.net/2011/07/11/dropbox-data-format-deduplication/ https://news.ycombinator.com/item?id=2478757 https://news.ycombinator.com/item?id=2478567 http://razorfast.com/2011/04/25/dropbox-attempts-to-kill-open-source-project/
Thoughts on this idea?