It looks like some of the Matrix devs were thinking about using IPFS for the Matrix "media" repository. It's basically an object store where the Matrix server keeps images and videos and files.
Coincidentally, that spec change proposal looks to have been posted exactly one year ago today. Doesn't look like there's anything concrete yet, but still there's obvious opportunities for combining a content-addressable object store API with a distributed content-addressable file system back end.
https://github.com/matrix-org/matrix-doc/blob/travis/msc/ipf...
Haven’t tried developing for matrix yet but I’m intrigued by its inertia right now.