Most focus groups offer some level of compensation. Normally token, but enough to show the person has received something for their input.
It’s about benefit/detriment – If you ask them and they give you their “intellectual property” in the form of an opinion, you have received benefit. If they receive nothing in return (even token) they leave the door open to receive benefit later on. If they take a “free pen”, for giving you the opinion then they equaled the equation and effectively closed the door.
That being said, it’s really much easier (and cheaper) to have a participant sign an indemnification (or often called a “hold harmless”) waiver at the time you ask the questions. That gives you a simple paper trail that may overt many issues and hard feelings later on.
