However in my experience, the mere act of thrusting a legal document in front of someone and demanding they sign causes many people to re-think permission.
I am not a lawyer!
This short video shot at a recent VisibleGains conference where the subject of permissions came up.
I'm not offering legal advice here. Rather, I want to share a practical alternative. I simply ask the person I am about to interview if it's okay to post the video.
Then in the edit process, I save the video permissions and post the interview.
Steve Garfield also suggests asking the person to spell their name.
Interestingly, a few days after the VisibleGains conference, I was interviewed for a special segment to be aired on the MSNBC Your Business program on October 31, 2010 and the first thing the producer did was have me spell my name.
Image credit (without "no" symbol): Shutterstock / April Cat
Disclosure: I am on the VisibleGains advisory board.