Are you kidding me? I would love to see this contract that they are not allowed to post here.
On a slightly related subject, my uncle is a Circuit Court Judge and I have been told multiple times by him that is is IMPOSSIBLE to sign away your rights. One of those rights is the First Amendment. Now, I understand that you would not be allowed to post inside info that you have based on NDA's, but even if you did and you didn't bow to legal department, you would win in court if you had a halfway decent lawyer. The problem is most people would just do whatever they were told. You would however lose credibility and people wouldn't trust you and/or put you in a position where you would want to quit or never have the ability to leak something again.
For example: I worked at a athletic facility where participants were required to sign a waiver saying if they got hurt, the company was no responsible. Well a kid tripped while running and broke his ankle. His father was a lawyer and told the company that they were going to pay for all the medical bills. As an employee and hearing this, I thought the father was out of his mind. But the company called their lawyer and he told them to pay for all the medical bills stating that "you cannot sign away your rights so the company is still responsible." So hearing that from a a Circuit Court Judge, corporate lawyer and seeing a lawyer threaten over it. I tend to believe them. unfortunately, people don't understand their rights and the law well enough sometimes.