Very few of the libraries will be owned by an individual though - I would bet >99% are owned by an OEM or software house. That OEM probably isn't interested in suing facebook for a small amount, because if facebook blocked that OEM's phones, it would probably spell the end of the OEM.
If you build a custom AOSP from source and add a new system library or modify an existing system library that adds a proprietary algorithm or maybe even a poem/artwork that you wrote yourself and put a proprietary license/copyright on, maybe you could go after fb for illegally pirating/stealing your own copyrighted work? Probably wouldn't work if you do this just to poke fb knowing about this feature, but if you happened to work on custom AOSP roms for personal use before this feature became widely known, then it sounds like you might possibly have a good cause?
