Earlier quoted context omitted.
I'm not sure we can hold individuals responsible for signing these non-disparagement clauses. They often don't have a lawyer to review the paperwork and, I am sure, employers like Facebook aren't going to wait for a new hire to have a lawyer review that paperwork. There's a real pressure to sign everything with HR and get on to starting your new role. Plus the power imbalance.
If you can't hold individuals responsible for signing contracts on the premise that they might not read them, you've simultaneously invalidated most contracts, increased the cost to enter a contract (essentially subsidizing the law industry), and severely limited the ability for individuals to enter into contracts — not to mention infantilizing adults who are fully capable of reading a document before signing it. Fur…
I don't think we can hold people responsible for these types of contracts if they are under duress, for instance, under threat of the loss of their job. In this case the person signed in order to get the promised severance package, without which they wouldn't be able to continue with life-saving medical coverage, in my opinion that would also be under duress.