Earlier quoted context omitted.
This is a really good question. It seems a non-disparagement clause waives one's right to the first amendment. http://www.jaburgwilk.com/news-publications/what-is-a-non-di... Is this right?
Whenever I had to sign one after a lay-off I checked with lawyer friends first. They are not really enforceable.
If they're legally binding then that's still bad.