I have yet to see any story where a signer has claimed that they had to sign something improperly or be fired.  I will concede that it is possible that it has happened, but you'll have to post a link to convince me.  In most cases, I think it has been more of a matter of people sleepwalking through their jobs and not caring enough to raise any objections.  That's certainly the impression I've gotten from reading the depostitions of Jeffrey Stephan and others.  Would they have gotten fired if they raised objections to the process?  That's anybody's guess, but since they never raised any objections in the first place evidently, it's hard for me to see them as "under duress."

Bottom line, it is apparently not hard to find a person to willingly do any old thing you want for a paycheck.

I'm sure that we'll start hearing claims that they were under duress after they start getting named personally in lawsuits, but beware of those claims.