It seems that it shouldn't be hard for a lawyer to craft up a change to the ToS for the site that:
- Grants Ello the right to use/reproduce user content (a normal everyday part of ToS), BUT
that right does not survive a change to either the corporate charter or the ToS without being positively re-affirmed by the end user.
In other words, Ello can use/reproduce your posts, like they need to.
- If they change the charter, users need to re-affirm "yes, you can continue to use my existing content"
- If they change the ToS to remove that language going forward, users need to re-affirm "yes, you can continue to use my existing content"
Combine that with some language about "no change to ToS or corporate charter can be binding without a 90 day review period for users", and you've got something with some teeth.