I once had an employer who made all of their employees sign a contract
stating any technical thing they do while employed by the company is owned
by the company, regardless of whether it was done on the employee's time
and in the employee's home, and the employee isn't allowed to print
articles or speak in forums without the company's permission and, if
memory serves, content review.
Signing the contract was mandatory for continued employment. I refused and
was fired (1996). Since employment is usually "at will," companies, who
generally have the better legal resource position, can pretty much put any
restriction on you that they want. In the case of the IETF, while this
"thing" was going on there was an implicit chill and I silently
disappeared from forums and commitments.
The lesson I learned is to read and negotiate these things up front, and
be prepared to walk away.